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Inorganic Organometallic and Organic Analogues of Carbenes.

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80 -
-80 -
Fig. 44. Melting points of (0)cyclic phosphonitrile chlorides r2441, of
cyclic phosphonitrile fluorides [236], and of (A) cyclic dimethylsiloxanes [245].
interaction. The striking similarity between the melting
point curves in Fig. 44 may be a suggestion of isoelectronic structures, that is, tetrahedral positively charged
phosphorus and “tetrahedral” negatively charged nitrogen. The additional ionic bonding might explain
the shortening of the otherwise identical P-N
bonds without hindrance to the almost “free” rotation
which is suggested by the extreme flexibility [236,2461 of
these compounds. The bonding in cyclic phosphonitrile
halides has for a long time remained controversial; the
suggestion of electron delocalization and aromatic
character 12471 has been vigorously contested [248,*491,
one of the main counter-arguments being constancy [236,244,2491 of the far-ultraviolet absorption
along each of these series.
Received: April 20th, 1965; revised August 17th, 1966
Abscissa: Upper row, total number of ring members, N ; lower row,
number of monomer units, X .
(Fig. 44) [*I This is somewhat
surprising, since an analogous conformation for the
12-membered ring would have a severe transannular
[?45] W . Patnode and D. F. Wilcock, J. Amer. chem. SOC.68, 358
[*I Added in proof: Alternations of other properties of phosphonitrile derivatives with ring size have recently been observed,
e.g., complex formation with hexamethylbenzene (S. K. Das,
[A 548 IE]
German version: Angew. Chem. 78, 1070 (1966)
R. A . Shuw, B. C. Smith, and C. P.Thakur, Chem. Commun.
1966, 33) and basicity (C. E. Brion, D. J. Oldfield, and N. L.
Paddock, Chem. Commun. 1966, 226).
[246] A. C. Chapman and N. L . Paddock, J. chem. SOC.(London)
1962, 635.
[247] D. P. Craig and N.L.Puddock, Nature (London) 181, 1052
(1958); D.P.Craig, M.L.Hefferman, R.Mason, and N.L.Paddock,
J. chem. SOC.(London) 1961, 1376.
[248] M . J. S. Dewar, E. A. C. Lucken, and M . A. Whitehead,
J. chem. SOC.(London) 1960, 2423.
12491 B. Lakatos, A . Hess, S. Holly, and G . Horvdth, Naturwissenschaften 49, 493 (1962).
Inorganic, Organometallic, and Organic Analogues of Carbenes
This review deals with inorganic, organometallic, and organic compounds, as well as with
elements, that on the basis of their electronic structure and their reactions can be regarded
formally as analogues of carbenes. These “carbene analogues” include in particular the
compounds of monovalent boron, aluminum, nitrogen, and phosphorus; those of divalent
silicon, germanium, tin, and lead; atomic oxygen; atomic sulfur; and atomic selenium.
The preparation and chemical properties of the carbenes and their analogues are compared.
1. Introduction
The chemistry of carbenes has undergone a remarkable
development in recent years [1-61. The Unusual reactions
of these compounds are attributable to the fact that they
contain a carbon atom with a sextet Of electrons, two of
New address: D. I. Mendeleev Institute of Chemical Technology, Moscow.
[I] I. L. Knunyants, N. P. Gambaryan, and E. M. Rocklin, Usp.
Chim. 27, 1361 (1958).
[2] Ph. Miginiac, Bull. SOC.chim. France 1962, 2000.
[3] E. Chinoporos, Chem. Reviews 63, 235 (1963).
141 W . E. Parham andE. E.Schweirer,Org. Reactions13,55 (1963).
Angew. Chem. internat. Edit.
1 Vol. 5
/ No. I 2
which do not participate in the bonding. Depending on
the preparation of the carbenes, these electrons may be
in the unpaired (triplet) or paired (singlet) state. Owing
to the unsaturation, most carbenes are electrophilic “1.
BY addition of two electrons to complete the octet, the
carbene carbon atom reverts to the tetravalent state,
with formation of one (sp2) or two (sp3) new bonds.
[5] W . Kirmse: Carbene Chemistry. Academic Press, New YorkLondon 1964.
[6] J. H i m : Divalent Carbon. Ronald Press, New York 1964.
[7] Some so-called nucleophilic carbenes appear to be exceptions; see, e . g . , H.-W . Wunzlick, Angew. Chem. 74, 129 (1962);
Angew. Chem. internat. Edit. I, 75 (1962); W . Kirmse, Liebigs
Ann. Chem. 666, 9 (1963).
Many other elements have an electronic structure
similar to that of carbene carbon atoms. Volpin et al. [a]
characterized the “electronic analogue” of the carbenes
by the following criteria:
lysis of chlorides of trivalent boron, such as BC13, B2C14,
or (BCl)4 [131.
+ :BCl -l-Clp
1. At least one lone pair of s or p electrons (or two unpaired electrons) on the central atom;
2. at least one unoccupied p orbital (or two electrons in
two p orbitals);
The :BCI liberated in this way has a life of about 0.01
sec [121, and can undergo insertion into the B-CI bond
as well as cyclopolymerization [I31 and oxidation [12al.
3. no unoccupied d level with a quantum number lower
than that of the valence p electrons.
These features are found in the elements of Groups I1
and VI of the periodic system, as well as in compounds
of the monovalent elements of Groups 111 and V, the
bivalent elements of Group IV, and a few cations (e.g.
R*N+, ROf, RS+, Clf, Br+. However, many of the
molecules and atoms mentioned react quite differently
from the carbenes, whose characteristic property is the
formation of one (sp2) or two (sp3) new covalent bonds.
This chemical property will be regarded as a fourth
criterion for carbene analogues.
For example, all cations of the types RzN+, RO+, Cl+ simply
form a single (sp3) covalent bond by accepting a pair of
electrons from another atom or ion. These cations cannot be
regarded as carbene analogues. The metals of Group I1 again
satisfy only the first three conditions. They react with acids
and halogens to form ionic salts. The metal M loses the
valence electrons to form the cation M*+, a reaction not
observed with carbenes. Though Mg, Ba, and Ca react with
aryl and alkyl halides to form compounds RMHal, corresponding to the insertion of carbenes into the C-Hal bond,
the similarity is purely formal.
Thus of the numerous electronic analogues of carbenes,
practically only a few compounds of elements of Groups
111to V and the elements of Group VI in the atomic state
remain as “chemical” analogues of carbenes. The present review deals with the preparation and properties of
these compounds, and reactions that could proceed via
such carbene analogues are also discussed.
0 2
In the spontaneous dismutation of B2Cl4, which probably also proceeds via :BCI, Urry et al. [I41 obtained not
only the cyclotetramer (BC1)4, but also stable free
radicals of the composition (Bl.0CIo.9-1.~)~
and with a
molecular weight of 650-750. These radicals are probably present as chains CIB-(BC1),-2-BCI.
By analogy with the formation of :BCI, it may be assumed
that the polymers (BH), formed by an electric discharge in
diborane/hydrogen at a pressure of 10-15 mm Hgrlsl result
from the polymerization of borene, :BH.
+ [:BH]
+ l/n(BH)n
This assumption is supported by the formation of the analogous methylene (:CHz) from hydrocarbons in an electric
discharge [I].
The reaction of organoboron dichlorides RBC12 with alkali
metals probably also proceeds via carbene analogues :BR.
For example, when C6H5BC12 is heated with sodium, potassium, or a potassium-sodium alloy in toluene or xylene, the
polymer (BC6H5)n (n = 9-12) is obtained [161, evidently
from the initially formed monomeric phenylborene, :BCsH5.
The possibility of such a mechanism is suggested in particular
by the formation of carbenes by the action of alkali metals on
di-, tri-, and tetra-halogenomethanes [171.
2. Carbene Analogues with Elements of Group 111
b) Aluminum Compounds
Boron Compounds
Carbene analogues of the type :BR (R = halogen or H)
are formed when energy is supplied to compounds of
trivalent boron. For example, the action of a highvoltage or high-frequency electric discharge on BCl3
vapor, without[9.10] or with added inert gas (argon,
helium) [Ill, liberates :BCI, which was identified by its
absorption and emission spectra. :BCl is formed also
by U V discharge in BCl3
12al and during flash photo[8] M. E. Volpin, Yu. D . Koreshkov, V. G. Dutova, and D . N.
Kursanov, Tetrahedron 18, 107 (1962).
191 B. A. Thrush, Nature (London) 186, 1044 (1960).
[lo] E. Miescher, Helv. physica Acta 8, 279 (1935).
[ll] G . Pannetier, P. Goudmand, 0. Dessaux, and I. Arditi, C. R.
hebd. SCances Acad. Sci. 258, 1201 (1964).
[12] D . Maeder, Helv. physica Acta 16, 503 (1943).
[12a] D . J. Knowles and A . S . Buchanan, Inorganic Chem. 4,
1799 (1965).
The monohalides of aluminum, :AlHal, are formed in
the same way as :BCI when a UV discharge in a hydrogen discharge tube is passed through AlBr3 vapor [121,
or by a high-frequency discharge in AlCl3, AIBr3, or
AII3 vapors [lo]. The lifetime of :A.lBr is approximately
0.01 sec [121.
[13] A . G. Massey and J. J. Zwolenik, J. chem. Soc. (London)
1963, 5354.
[14] G. Vrry, E. P. Schram, and S. I. Weissman, J. Amer. chem.
SOC.84, 2654 (1962).
[15] A . Stock and W. Mathiny, Ber. dtsch. chem. Ges. 69, 1469
[16] W. Kuchen and R.-D. Brinkmann, Angew. Chem. 72, 564
(1960); 2. anorg. allg. Chem. 325, 225 (1963).
[17] 0. M . Nefedov, A . A . Ivasshenko, M . N . Manakov, W. I.
Shiryaev, and A . D . Petrov, Izvest. Akad. Nauk SSSR, Otdel.
chim. Nauk 1962, 367; 0. M. Nefedov and A . A . lvashenko,
Doklady Akad. Nauk SSSR 156, 884 (1964); Izvest. Akad. Nauk
SSSR, Ser. chim. 1965, 2209; 0. M. Nefedov and W. I. Shiryaev,
Z . obSE. Chirn., in press, see there for further literature.
Angew. Chem. internat. Edit. / VoI. 5 (1966)
1 No.
3. Carbene Analogues with Elements of Group IV
SiC14+ H2
sic14i- Sic
a) Silicon Compounds
The compounds of bivalent silicon and germanium are
of great interest from the point of view of carbene
chemistry. In contrast to halogenocarbenes, which are
readily formed by the action of strong bases (ROM or
RLi) on halogenomethanes [41, :SiHHal and :SiHal2
cannot be prepared from H2SiHal2, HSiHal3, or SiHal4.
These compounds give products formed by nucleophilic substitution of the halogen and even of the H
atoms by the group RO or R of the reagent used,
probably due partly to the fact that the Si-H and
C-H bonds are polarized in different directions (e.g.
80 80
Whereas CH4 and CCl4 decompose into carbon and
hydrogen or chlorine at 8OO-90OoC, Sic14 at 900°C
gives a gas mixture with an intense absorption maximum
at 3150 A. Similar spectra are given by SnC12 and PbCl2
(A,,, = 3100 A). From these observations and from
thermodynamic calculations, it was concluded [I91 that
Sic14 decomposes to :Sic12 and chlorine. Similarly,
:Sic12 is formed from Sic14 and silicon at high temperatures f191; it reacts further with silicon to SiCI.
2 :Sic12
2 Si
c 4SiCI
Angew. Chem. internat. Edit. Vol. 5 (1966)
No. 12
Better yields of dialkyldichlorosilanes and alkyltrichlorosilanes are obtained in the “direct” synthesis when copper is
added to the silicon [231. This catalytic action is attributed 1231
to the formation of cuprous chloride in the reaction zone;
this reach with silicon to form :SiC12, which is then converted
into the organochlorosilanes:
[18] C. Eaborn: Organosilicon Compounds. Butterworths, London 1960.
[19] K . Wieland and M . Heise, Angew. Chem. 63, 438 (1951).
[20] E. G. Rochow and R . Didtschenko, J. Amer. chem. SOC.74,
5545 (1952); and literature cited there.
1211 H . Schuifer and J. Nickl, Z . anorg. allg. Chem. 274, 250
[22] H . Schafer, Z . anorg. allg. Chem. 274, 265 (1953); and
literature cited there.
[23] S . A. Golubzov, K . A . Andrianov, et a/., Doklady Akad.
Nauk SSSR 151, 1329 (1963); and literature cited there.
[241 J. Joklik and V . Baiant, Collect. czechoslov. chem. Commun. 29, 603, 834 (1964).
+ Si,C12,,2
CH3Clf :Sic12
+ cH3cl.C~
2CuCI+ CH4-t C + H2
+ 2CuCl
CH3Cl.Cu+ CH&%
For example, the high-temperature process for the preparation of chlorosilanes from carborundum (Sic) and Sic14
vapor diluted with a carrier gas such as H2 or N2 is based on
the reactions [221:
+ :Sic12
The formation of a mixture of lower silicon chlorides,
e.g. of average composition SiC12.61, when silicon and
tetrachlorosilane are heated together to about 1000“C
was observed by other authors [201. Schu/er and Nicklt211
showed by kinetic and thermodynamic studies that the
reaction of Sic14 with Si begins at 800 “C and is reversible. The heat and entropy of formation of gaseous
:Sic12 are 29.9 kcal/mole and 71.1 cal mole-1 deg-1,
respectively, at 298 “K [211. The intermediate formation
of :Sic12 is the basis of most high-temperature methods
for the preparation of chlorosilanes and organochlorosilanes from silicon or its alloys [22-241. Under the conditions used, the silicon dichloride readily undergoes
insertion into chemical bonds, such as H-CI, C-CI, or
Si-Cl bonds to give compounds of tetravalent silicon.
2 :sic12
For the preparation of higher chlorosilanes SinC1zn+2,the
reaction mixture must be quenched, since :Sic12 disproportionates on slow cooling to Si and Sic14 [21J.
The “direct” synthesis of trichlorosilane and organochlorosilanes from silicon and hydrogen chloride or organic chlorides also proceeds via :SiC12[23.241. On the basis of the rate
of formation of HSiC13 from Si and HCI and of the influence
of the addition of HCI on the “direct” synthesis of methylchlorosilanes, Joklik and Buinnt “1 proposed the following
reaction scheme:
Si + :SiC12+ H2
CH,Cl.Cu+ :SIC12
SiCI4+ Si
:Sic]*+ 2HCI
+ :Sic12
+ :Sic12
SiC14+ (n-1) :Sic12
88 88
H-Sic13 and H-CCl3) and partly to the stronger ionic
character of the Si-Hal bond [181.
+ :Sic12
: SiC12+ 2Cu
CH,SIC12+ CuCl
(CH3)2SiC12+ CuCl
+ Cu
The above scheme is confirmed by the increase in yield of
(C2H5)2SiC12 from C ~ H S Cand
I silicon when small quantities
(ca. 2%) of CuCl are added to the silicon, and by the increase
in yield of C2HSSiCI3 when larger quantities ( 9 2 %) of CuCl
are added [241.
The feasibility of the formation of :Sic12 under the conditions
of the “direct” synthesis (300-400 “C) was confirmed by
thermodynamic calculations 123 251. :Sic12 has been detected
by mass spectrometry in the gaseous products of the reaction
of Si with CuCl at 18O-20O0C[251.
According to thermodynamic calculations and kinetic
measurements, :Sic12 also occurs as a n intermediate in the
preparation of Si by reduction of tri- and tetrachlorosilanes
with hydrogen at 1000-2000°K [261.
Whereas carbenes readily form dimers, no dimerization
has been observed in the case of :SiC12, which telomerizes or polymerizes in the absence of electron acceptors. For example, SiloC122, Si2oC142, and Si25C152
were obtainedr271 by the decomposition of Sic14 in an
atmosphere of nitrogen or hydrogen at 1000-1250 “C.
In addition to SiCl4, HZcan also act as a telogen in this
reaction, as is shown by the formation of SiloCl2oH2
[25] W. I. Zubkov, M . W . Tichomirova, K . A . Andrianov, and
S. A . Golubzov, Doklady Akad. Nauk SSSR 159, 599 (1964).
[26] E. Sirtl and K . Reuschel, Z . anorg. allg. Chem. 332, 113
(1964); J. Niederkorn and A . Wohl, Rev. roum. Chim. 11, 85
[27] R . Schwarr et a/., Z. anorg. allg. Chem. 232, 241 (1937);
Chem. Ber. 80, 444 (1947); also literature cited there.
and Si5CllOH2 from S i c 4 in an atmosphere of hydrogen
at 1150 to 125OoC[27,281.
Similar polychlorosilanes having the composition
SiC12.05-2.30, which may also be regarded as telomerization products of :Sic12 and Sic14 or Si2C16, &re
formed from hexachlorodisilane in the presence of trimethylamine or trimethylammonium halides at 80 to
100 "C[291 or in the presence of 2 % of triethylamine in
vacuum at room temperature 1301.
n Si2C16
-+ C13Si-(SiC12)n-C1+
The thermal decomposition of C2H5-SiClz-SiC13 in the
presence of (CH3)3N.HCl leads similarly to (SiC12), and
CzH5-SiC13 1291; (SiCll.& is formed when Si2Cl6 is heated
with traces of (C2H5)3N[301. The occurrence of :Sic12 as an
intermediate in the decomposition of compounds of the type
RSiC12-SiCI3 (R = C1 or alkyl) is suggested not only by the
composition of the resulting polymers, but also by the formation of dichlorocarbene when compounds of the type
RCClz-SiC13 are heated [311.
The thermal reaction of Sic14 with Si has been used for the
preparation of polymeric (SiClz), (n = 12-17) in the form of
transparent, colorless or slightly yellow resins, which are
readily soluble in organic solvents [32,331. The probably
cyclic (SiC12), is formed above 900°C, the yield and molecular weight increasing with rising temperature (n increases
from 12 at 90OoC to 16 at 12OO0C)[331.The polymers prepared reduce AgNO3 and SbC13 to the metals, and decompose to low molecular weight fragments [(SiC12),-, to
Similarly, when silicon tetrabromide is passed over
silicon at 1200 "C in a high vacuum, the two substances
form silicon dibromide :SiBrz, which has been isolated
in the polymeric form 1343. Reduction of the polymeric
(SiBr& with LiAIH4 led to polymeric silylene ( S ~ H Z ) ~ ;
alkylation with alkylmagnesium bromides gave polydialkylsilylenes (SiR2)n (R=CH3, C2H5, n-C3H7, or
n-C4H9); and hydrolysis gave a polymeric acid of
average composition Si(0H)z.z.
Silicon difluoride can be prepared similarly to :Sic12
and :SiBr2. SiF4 vapor is led through a quartz tube
packed with silicon powder at 1150-1200 "C in a high
vacuum (residual pressure 0.04-0.2 mm Hg) [35,361.
:SiF2 can also be prepared from carborundum (Sic) or
calcium silicide (CaSi2). Silicon difluoride exists as the
monomer at -196°C. Above -80°C it gives a plastic
polymer (SiFZ),, where n I
16. The "half-life" of gaseous :SiF2 at room temperature is ca. 150sec., i.e. at
least 100 times greater than that of most carbenesc361.
[28] R. Schwarz and R . Thiel, Z . anorg. allg. Chem. 235, 247
(1938); R. Schwarz and A . Koster, ibid. 270, 2 (1952).
[29] C. J. WiIkins, J. chem. SOC.(London) 1953, 3409.
[30] A . Kaczmarczyk and G. Urry, J. Amer. chem. SOC.82, 751
(1960); also literature cited there.
[31] W . I. Bevan, R. N . Haszeldine, and J . C. Young, Chem. and
Ind. 1961, 189.
[32] M . Schmeisser and P. Vuss, Z . anorg. allg. Chem. 334, 50
(1964); see there for further literature.
[33] P. W . Schenk and H . Bloching, Z . anorg. allg. Chem. 334,
57 (1964); see there for further literature.
1341 M . Schmeisser and M . Schwarzmann, Z. Naturforsch. l i b ,
278 (1956).
[35] D . C. Pease, US-Pat. 2840588 (24 June, 1958), Chem. Abstr.
52, 19245 (1958).
[36] P. L . Timms e f al., J . Amer. chem. SOC.87, 2824 (1965).
According to Schmeisser and Ehlers [371, however, silicon
difluoride prepared in this way, both in the monomeric
and polymeric states, contains appreciable quantities of
oxygen (w0.3 atoms per atom of Si) derived from the
quartz. :SiF2 that is completely free from oxygen is
formed on pyrolysis (700 "C) of hexafluorodisilane in a
high vacuum [371.
:SiF2+ SiF4
Polymeric (SiF& is also obtained by the action of
magnesium on dibromodifluorosilane in ether [381. Probably, free :SiF2 is involved as an intermediate by analogy with similar reactions of CF2Br2 and CF3Br [391.
The (SiF2)n polymer generates on heating in vacuum to
200-400 "C all perfluorosilanes from SiF4 to Si14F30 and
a (SiF), polymer or silicon. With 20 % aqueous hydrofluoric acid (SiF& forms silanes from SiH4 to at least
SisH14 plus much hydrogen [361.
:SiF2 reacts with BF3 or BCl3 at liquid nitrogen
temperatures to form insertion products of type
Hal2B(SiFz),Hal, where n = 2-4 and Hal = F or C1139al.
Under the same conditions :SiF2 inserts readily into
C-F bonds of trifluoroethylene [3gbl and of perfluorobenzene [39cl.
:SiFz +
Addition of :SiF2 to ethylene, acrylonitrile, 2,3-dimethyl-l,3-butadiene, and tetrafluoroethylene has been
effected at -196"C, the reaction with the last of these
compounds leading to a solid polymer contclining
SiFz-SiF2-CF2-CF2 groups [35,39bl.
Reaction of silicon difluoride with ethylene gives,
among other products, cyclic adducts and some
C2H4SiF2 [39bl.
H Z C = C H z + :SiF2 -w
Benzene and toluene give with :SiFz compounds of
type ArH(SiFZ),, where n = 2 to 8, in particular bicycles with (SiF2)3 bridges [3gCl.
[37] M . Schmeisser and K.-P. Ehlers, Angew. Chem. 76, 781
(1964); Angew. Chem. internat. Edit. 3, 700 (1964).
[38] M . Schmeisser, Angew. Chem. 66, 713 (1954).
1391 V. Franren and L. Fikentscher, Chem. Ber. 95, 1958 (1962);
V. Franzen, ibid. 95, 1964 (1962).
[39a] P. L. Timms e f al., J. Amer. chern. SOC.87, 3819 (1965).
[39b] J. C. Thompson, J . L . Margrave, and P. I,. Timms, Chern.
Commun. 1966, 566.
[39c] P. L. Timms, D. D . Stump, R . A. Kent, and J . L. Margrave,
J. Amer. chern. SOC.88, 940 (1966).
Angew. Chem. internat. Edit.
/ VoI. 5 (1966) / No. 12
by reaction with metals. Kipping et al.[45J obtained
polymers [(C6H5)2SiIn from diphenyldichlorosilane and
R = H, C H3
Infrared studies of silicon difluoride and its reactions
with BF3, 0 2 , CO, NO, and other molecules in lowtemperature matrices at 20-50 "K indicates the occurrence of a reactive species, probably (SiF2)z [39dl.
Polymeric silicon diiodide, (Sir&, a solid, amorphous,
orange substance, was obtained (401 when SiI4 was
passed over silicon in a high vacuum at 800-900°C
(yield ca. 1%). A similar polymer, (Si12.&, which is
insoluble in the common organic solvents was obtained
in a yield of 60 t o 70% when a glow discharge was
passed through Sil4 vapor in a high vacuum[401.
In a high vacuum at 220-230 "C, ( S i 1 2 . ~ changes
(SiI&, from which polymeric silicon mixed dihalides
can be prepared by treatment with chlorine or bromine
in benzene at -30 t o +25 "C[40J:
The benzene-soluble polymer (Sir& probably is also
formed in the pyrolysis of Sir4 in high vacuum a t 800
to 900 "C 1401.
High-temperature reactions of silicon tetrahalides with
silicon and the pyrolytic decomposition of hexahalogenodisilanes SizHa16 or tetrahalogenosilanes SiHal4 are general
methods for the preparation of silicon dihalides, :SiHalz. In
contrast to :SiHalz, dichlorocarbene cannot be prepared from
CC14 and activated charcoal at 1200-1300 "C [411. Kinetic
investigation of this reaction with the aid of mass spectrometry shows that :CC12 does not occur as intermediate"Q1.
Silicon(r1) dihalides are formed from halogen compounds of
tetravalent silicon not only on heating, but also by the action
o f other sources of energy. For example, the telomers
and SisC114 have been prepared with the aid of a glow
discharge in a mixture of gaseous HSiCI3 and H2 1431. Passage
of a mixture of Sic14 and H2 through a glow discharge between A1 electrodes (10000 V) in vacuum results in solid
polymers of (SiCI& and (SiH& [43al. On flash photolysis of
H3SiCI or HsSiBr, the fragments :SiHCI or :SiHBr occur in
the absorption and fluorescence spectra in the region 4100 to
6000 8, [441.
Organic compounds of bivalent silicon and polymers
thereof are obtained, unlike the halogen compounds,
[39d] J. M . Bassler, P. L. Timms, and J. L. Margrave, Inorganic
Chem. 5, 729 (1966).
[40] M . Schmeisser and K. Friederich, Angew. Chern. 7 6 , 782
(1964); Angew. Chern. internat. Edit. 3 , 699 (1964).
[41] M . Schmeisser, H. Schroter, and H. Schilder, Chem. Ber. 95,
1648 (1962).
[42] D . R. Bidinosti and R. F. Porter, J . Amer. chern. SOC. 83,
3737 (1961).
1431 A. Besson and L . Fournier, C. R. hebd. Seances Acad. Sci.
251, 2987 (1960); cf. also ibid. 150, 1118 (1910) and [I].
[43al R. Schwarz and G. Pietsch, 2 . anorg. allg. Chem. 232, 249
Angew. Chem. iiiternat. Edit.
/ Vol. 5 (1966) / No. I 2
liquid sodium in the absence of solvents or in boiling
toluene or xylene. Gilman et al.[461 later found that
these products, which are also formed in the reaction of
(C6H5)2SiC12 with sodium, lithium, or magnesium in
tetrahydrofuran, are essentially mixtures of the cyclopolymers [(C6H5)2Siln having n = 41471, 5, 6, and much
greater than 6.
In our opinion the formation of these products may be
attributed to cyclopolymerization of the intermediate diphenylsilylene which, unlike diphenylcarbene (formed e.g.
from (CsH5)2CC12 and lithium [171), cannot dimerize. However, recent attempts [481 to identify (CsH5)2Si:, which may
be formed from (C,jH5)2SiC12 and lithium, by addition to
cyclohexene were unsuccessful. 1491.
Other diaryldichlorosilanes, e.g. (p-CH3-C6H4)2SiC12[5°1,
as well as phenoxydiphenylchlorosilane [SlI react with sodium
in the same way as (CsH&SiCh.
Dialkyldichlorosilanes also react with alkali metals.
Thus t h e reaction of (CH&SiC12 both with liquid
sodium in benzene a t 115-200 "C and ca. 16 atm 1521
and with lithium in tetrahydrofuran at 250°C and 50
atm [531 leads to a mixture of thepolymer [(CH3)2SiIn( I ) ,
where n w 55, with dodecamethylcyclohexasilane (2) 1541.
(2) 0.05-2.570
The polydimethylsilylene [(CH3)2SiIn ( I ) , whicb is
insoluble in organic solvents, and the cyclohexasilane
(2) 1541 were obtained in a total yield of 90-97
by the
[44] G. Herzberg and R. D. Verma in: Symposium on Molecular
Structure and Spectroscopy,Columbus, Ohio, 1963, p. 49; cf. also
[45] F. S. Kipping and J. E. Sands, J . chern. SOC.(London) 119,
830, 848 (1921); F. S. Kipping, ibid. 123, 2590, 2598 (1923); 125,
2291 (1924); I927, 2719; F. S. Kipping and H . E. Murray, ibid.
1929, 360.
[46] H. Gilman and G. L. Schwebke, Advances organometal.
Chem. I , 89 (1964); and literature cited there.
[47] The primary product of this reaction is probably octaphenylcyclotetrasilane (see [39]). According to E. Hengge, H. ReittPr,
and R. Perzold [Z. Naturforsch. 186, 425 (1963)l this compound
exists in two stereoisomeric forms.
[48] H. Gilman and D. J . Peterson, J . Amer. chern. SOC.87, 2389
[49] Monoaryl- and particularly diarylcarbenes also have very
low activities in electrophilic additions to double bonds; see e.g.
[5,17]. Diphenylcarbene (from (C~H&CCIZ
and Li ir, tetrahydrofuran) cannot even add to cyclohexene at -10 to 30 "C [ O . M .
Nefedov and V. I. Shiryaev, 2. obSi.. Chirn., in press].
[50] A. R. Steele and F. S . Kipping, J . chern. SOC.(London) 1929,
2545; and literature cited there.
[511 F. S. Kipping, J . chern. SOC.(London) 1927, 2728.
[ 5 2 ] C. A . Burkhard, J . Arner. chem. Soc. 71, 963 (1949).
[53] E. Hengge and H. Reuter, Naturwissenschaften 49, 514
[54] According to [53,60] the crystal form of ( 2 ) changes at
74 "C, and the compound sublimes above 120 "C, m.p. ~ 1 4 "C.
However, the publications [57,58] give m.p. 228-231 "C (with
slight sublimation) and 248-250 "C (with preliminary heating of
the block to 24OoC), respectively, in agreement with the data
reported by H. Gilman and R. A . Tornasi [ J . org. Chemistry 28,
1651 (1963)l.
reaction of (CH3)2SiC12 with lithium or sodium in
tetrahydrofuran at atmospheric pressure between -60
and +70 "C 155-591. This reaction yields linear and cyclic
polymers in the ratio of from 9 : l to 1:3, depending on
the conditions [57,581, The reaction of dimethyldichlorosilane with an Na/K alloy in boiling tetrahydrofuran
proceeds similarly (yield of ( I ) 13 %, of (2) 81 % 1601.
(CH3)3Si-Si(CH3)2H (30%)
+ (CH,),SiH
H e , 200 m m
Similar products, i.e. t h e polymer [(CzH5)2 Si],, which is
insoluble in organic solvents, a n d a crystalline cyclopolymer
probably having t h e composition [(C*H&Si]6 or greasy o r
liquid polymers of the general formula [(C2H5)2SiIn, a r e
formed in t h e reaction of (C~H5)2SiClzwith lithium in tetrahydrofuran [56,58,591 or with sodium in boiling xylene [611 or
toluene with added ethyl acetate [621.
By analogy with the reactions of halogenomethanes
with lithium or lithium alkyls, in which carbenes are
formedI631, R2Si: is assumed to occur as intermediate
in the reaction of dialkyldichlorosilanes with lithium or
sodium [55,56,58,591.
2 Li
The unstable primary products (3) and (4) can not only
be stabilized by isomerization to form dimethylvinylsilane (5) or by dimerization to form the heterocycle
(6), but also by further reactions of (4) with ethylene
[55] 0. M . Nefedov, M. N . Manakov, and A . D . Petrov, Izvest.
Akad. Nauk SSSR, Otdel. chim. Nauk 1961, 1717; 1962, 1228.
[56] 0. M . Nefedov, M . N . Manakov, and A . D . Pelrov, Plaste u.
Kautschuk 10, 721 (1963).
1571 0. M . Nefedov, G. Garzo, T. Szdkely, and W. I. Schiryaev,
Doklady Akad. Nauk SSSR 164, 822 (1965).
[58] 0. M. Nefedov, W. I . Schiryaev, M. N . Manakov, et al.,
obSE. Chim., 'in press; M. N . Manakov, Dissertation, Mcscow
[59] 0. M. Nefedov, T. Szdkely, et al. in: Internat. Symposium
on Organosilicon Chemistry, Sci. Commun. Prague 1965, p. 65.
[60] U. Graf zu Stolberg, Angew. Chem. 75, 206, 347 (1963);
Angew. Chem. internat. Edit. 2, 150 (1963).
[61] Brit. Pat. 671774 (7 May 1952); Chem. Abstr. 46, 8895
[62] A . D . Petrov, W . F. Mironov, and W . G. Gluchovzev, obSE.
Chim. 27, 1535 (1957).
[63] See [5,17] and particularly [39], as well as 0. M . Nejedov and
R. N . Shafran, Izvest. Akad. Nauk. SSSR, Ser. chim. 1965, 538.
As was recently shown [G. Kobrich, K . Flory, and W. Drischel,
Angew. Chem. 76, 536 (1964); Angew. Chem. internat. Edit. 3,
513 (1964); W. T . Miller and D . M. Whalen, J. Amer. chem. SOC.
86, 2089 (1964)], compounds of carbon similar to RZ(Li)SiCI,
e.g. LiCHC12 and LiCCI3, are stable only a t low temperatures
(below -60 "C, generally from -1 10 to -1 15 "C).
[64] With a two- to threefold excess of (CH3)2SiC12, as with an
excess of lithium, an extremely insoluble polymer ( I ) (yield 80%)
and the cyclohexamer (2) (yield ca. 10%) are formed together
with a very small quantity of linear a,w-dichlorodi- and trisilanes
(1-1.5%); see [58]; cf. S. M . Shivukhin et al., Z . obSE. Chim. 33,
3274 (1963).
[65] P . S. Skell and E. J. Goldstein, J. Amer. chem. SOC.86, 1442
[66] 0. M . Nefedov and M . N . Manakov, Angew. Chem. 76, 270
(1964); Angew. Chem. internat. Edit. 3, 226 (1964).
Schemc 1
and dimethylsilylene to form 1,I-dimethyl-1-silacyclopentane (7) and a copolymer (8), respectively.
Scheme 1 shows a number of reactions that offer evidence of the intermediate formation of dimethylsilylene,
(CH&Si:. These include the reaction of lithium with
excess of dimethyldichlorosilane [641 and the addition
of dimethylsilylene to trimethylsilane [651, to ethylene,
and to a number of other olefins (isobutylene, l-heptene, cyclohexene) [56,58,59965,661.
M = L1, N a , K
The dimethylsilylene prepared in this way, which is
probably in the singlet state, is characterized by low
reactivity in electrophilic additions (e.g. the yields of
(6), (7), and similar adducts are generally 2 to 10%).
This can be attributed to the stabilizing influence of the
unoccupied d orbitals of the silicon atom. In contrast
to the alkylcarbenes, which very readily undergo the
carbene-olefin or carbene-cyclopropane isomerization 15 $1 [*I, dimethyl- and other dialkylsilylenes isomerize only to a maximum extent of 5 % or not at
all [57-59,651.
Dimethylsilylene is also assumed to be involved in the
formation of the unsaturated heterocycle (9b) [671 from
tolan, (CH&SiC12, and sodium in boiling xylene [8,68,691.
/s1\ C - C &
(9b), 0.5-5%
[ *] The carbene-olefin and carbene-cyclopropane isomerizations
may be illustrated by the equation
[67] It was originally assumed that (9a) is formed from (CH3)zSi:
and tolan, whereas its dimer (96) is actually formed. See [68,69],
and N . G . Bokii, 2. strukturnoy Chim. 6, 476, 571 (1965).
[68] R . West and R . E. Bailey, J. Amer. chem. SOC.85,2871 (1963).
[69] F. Johnson, R . S . Gohlke, a n d W . A . Nasutavicus, J. organometal. Chem. 3, 233 (1965).
Angew. Chem. internat. Edit.
1 Vol. 5 (1966) / N o .
with benzyne,
and its polymerization and addition to tolan was
achieved [71al.
Dimethylsilylene probably is also formed, together
4 2RSiR;
2RMgBr + 2BrSiR;
with dimeric and polymeric biradicals ( l o ) , in the
pyrolysis of polymeric dimethylsilicon ( I ) in an inert
9 RiSiMgBr
[:SIR;] + I/n(SiR;)n
atmosphere W57-59.66J. In the presence of acceptors
R = sec-CdHs, tert-CdHp; R' = Br or R.
(ethylene, tolan), adducts are formed; in the absence of
acceptors, the biradicals recombine to give cyclic and
Dimethylsilylene was obtained C711 by thermolysis of
polymer [(CH3)2SiIx.
adducts of 1,1-dimethyl-2,3,4,5-tetraphenyl-l-silacyclopentadiene with alkynes, e. g. benzyne or phenylacetb) Germanium Compounds
Monomeric and polymeric compounds of bivalent
silicon can be obtained by the action of Grignard compounds having bulky substituents on broniosilanes 1701.
Germanium difluoride and particularly germanium diiodide, unlike the corresponding carbon and silicon
dihalides, are stable even in the monomeric state.
"Monomeric" here refers to the gaseous state; Gel2
crystallizes in the brucite lattice, m.p. 48.5 "C. Solid
GeF2 is orthorhombic, m.p. 111"C.
The classic preparation of germanium diiodide is the
partial reduction of germanium tetraiodide with hypophosphorous acid1721 (75 % yield):
GeI2 is also formed 1731 by the spontaneous decomposition of the unstable triiodogermane, which is prepared
by exchange reactions from HGeC13 or its ether adducts 1741.
HGeC1, A
The dimethylsilylene prepared in this way also adds to
ethylene and other olefins to form heterocycles and
linear hetero compounds of the type (5) to (8)[591.
Dimethylsilylene polymerizes to give, in the absence of
acceptors, the polymer ( I ) 1711. Similarly diphenylsilylene was prepared from the adduct of 1,1,2,3,4,5-
+ HI
Despite its stability, GeI2 undergoes many reactions
characteristic of carbenes and their analogues, though
under more vigorous conditions. In particular, it
inserts into C-I bonds [75-771. This reaction is carried
out in a sealed tube or in an autoclave.
Coz(C0)~ GeI2
20". 10 min
-- -
-+ RCHzGeI3
80-140° C
80-90 %
C ~ H S I +GeIz
+ GeIz
+ (CF3)ZGeIZ
d CF3GeI3
135 C
43 %
R = H, C H ~ C J HCH30,
[70] G . Schott and J. Meyer, Z. anorg. allg. Chem. 313, 107
[71] H. Gilman, S . G. Cottis, and W . H . Atwell, J. Amer. chem.
SOC.86, 1596 (1964).
[71a] H. Gilman, S. G . Coftis, and W. H . Atwell, J. Amer. chem.
SOC.86, 5584 (1964).
Angew. Chem. internat. Edit.1 Vol. 5 (1966) 1 No. I2
[72] E. A . Flood, L. S . Foster, and E. W. Pietrusza, Inorg. Syntheses 2, 106 (1946); 3, 63 (1950).
[73] T. K . Gar and W . F. Mironow, Izvest. Akad. Nauk SSSR,
Ser. chim. 1965, 855; also literature there cited.
[74] 0. M . Nefedov, S . P. Kolesnikov, and W . I. Shevychenkc,
Angew. Chem. 76, 498 (1964); Angew. Chern. internat. Edit. 3,
508 (1964); Doklady Akad. Nauk SSSR 162, 589 (1965).
[75] E. A. Flood, J. Amer. chem. SOC.55, 4935 (1933); E. A .
Flood, L. S. Fosrer, and K . L. Godfrey, Inorg. Syntheses 3, 64
[76] M . Lesbre, P. Mazerolles, and G. Manuel, C. R. hebd.
Seances Acad. Sci. 257, 2303 (1963).
1771 H . C. Clark and C.J . Willis, J. Amer. chern. SOC.84, 898
:Sic12 [781 and the carbenes, particularly methylene "9,
801, react similarly with organic halides. Germanium
diiodide readily reacts with octacarbonyldicobalt 180al:
GeI2 also reacts with trialkyl- and triarylphosphines at
about 130°C to form adducts (11) that are formally
analogous to phosphoranes [821.
R3P+ GeI2
R3PGeI2 [81]
R = alkyl, aryl
Like the dihalogenocarbenes [5,831, Gel2 can add to CC
triple bonds [8J. Like their silicon analogues [671 the
germacyclopropenes (13) probably formed first are
unstable and are converted into stable heterocycles (14)
or polymers (12) [69,841.
GeF2 readily forms the GeF3' ion and its salts, e.g.
CsGeF3 [853. This formally corresponds to the equilibrium between dihalogenocarbenes and trihalogenomethyl anions [4,51:
:CHal2+ Hal"
It is assumed L731 that germanium dibromide also exists
as the monomer in solution. It is obtained in 56 to 65
yield by vacuum distillation of a solution of HGeBr3 in
aqueous hydrobromic acid or of a mixture with ether.
GeBr2 can insert into polarized C-halogen bonds, and
can add to CC triple bonds 1731:
+ GeBr;! + HzC=CH-CHz-GeBr3
65 %
Nascent ethylene (liberated from 1,2-diiodoethane at
150 "C in a sealed tube) adds to Ge12 to form a polymer
(CH2-CH2-GeI2), [761.
GeI2 can be added to isoprene and 2,3-dimethyl-l,3butadiene in 1,Cposition to form the corresponding
heterocycles [84al. This reaction with isoprene requires
3 hr at 60"C, that with dimethylbutadiene is exothermic.
The stable monomeric germanium difluoride is obtained
when germanium powder is heated with hydrogen
fluoride (225 'C, 16 hours, 93 % yield) 1851.
Ge+ 2HF
[78] See Section 3a, particularly [23,25].
[79] V. Franzen, Liebigs Ann. Chem. 627, 22 (1959).
[80]M . Hudlickj. and V. Konig, Collect. czechoslov. chem. Commun. 28, 2824 (1963).
[80a] D . J . Patmore and W. A. G. Graham, Inorganic Chem. 5,
1405 (1966).
[81] R. B. King, Inorganic Chem. 2, 199 (1963).
[82] See [ 5 ] , particularly p. 184.
obSi.. Chim. 34, 3845
[83] R . R. Kostikov and I. A. Dyakonov,
(1964); E. V. Dehmlov, Tetrahedron Letters 1965, 2317.
[84] M . E. Volpin er al., Izvest. Akad. Nauk SSSR, Ser. chim.
[963, 2067; further literature cited there; L . W. Vilkov et al.,
Z . fiz. Chim. 38, 2674 (1964).
[84a] P . Marerolles and G. Manuel, Bull. SOC.chim. France 1966,
327; cf. [73, 87, 891.
[85] E. L . Muetterfies, Inorganic Chem. I , 342 (1962).
[86] L . M . Dennis and A. W. Laubengayer, Z. physik. Chem. 130,
530 (1927); N . Bartlett and K . C. Yu, Canad. J. Chem. 39, 80
(1961). Cf. [21,32-341, particularly [35,36].
=+[2 R,O*H]"
+ GeHalz
HzC=CH-CH=CHz + GeHalz
GeF2+ H2
GeBr2 reacts with butadiene at room temperature to
give in 28 % yield l,l-dibromo-l-germa-3-cyclopentene
(15a), which is formally a 1,4-adduct 1871. Compound
(15a) 1731 or the dichloro derivative (15b) [74,88,891 is
also formed when butadiene is passed through the ether
adducts of tribromo- or trichlorogermane (16) [741. The
dichloro derivative (15b) is also formed, together with
2-butenyltrichlorogermane, by the reaction of butddiene with trichlorogermane [88,901. The formation of
germanium dihalides from trihalogenogermanes and
particularly from their ether adducts (16) is attributable
to the strong polarization of these compounds [74,89,911.
In addition to isomerization to the stable (15), the
unstable intermediate heterocycle ( I 7) forms oligomers
GeF2, like the silicon dihalides, also can be prepared
from germanium and tetrafluorogermane at or above
loo "C [861.
+ GeBrz
H CI = C € I
(ISa), H a l = B r
115b), H a l = C1
Ei = CzH,
[87] Products of the formal 1,4-addition to 1,3-butadiene are also
formed in reactions with other carbene analogues, e.g. :NH
[R.Appel and 0. Buchner, Angew. Chem. 74,430 (1962); Angew.
Chem. internat. Edit. I , 332 (1962)l and carbenes, e.g. :CHI and
:CC12 [ V . Franzen, Chem. Ber. 95, 571 (1962); B. Grzybowska,
J . H. Knox, et al., J. chem. SOC.(London) 1962,3826; M . Orchin
and E. C. Herrick, J. org. Chemistry 24, 139 (1959)l.
[88] 0 . M . Nefedov, S . P . Kolesnikov, A . S . Khatschaturov, and
A. D . Petrov, Doklady Akad. Nauk SSSR 154, 1389 (1964).
[89] 0. M . Nefedov and S . P . Kolesnikov, Izvest. Akad. Nauk
SSSR, Ser. chim. 1966, 201, and literature cited there.
[90] W. F. Mironov and T. K . Gar, Doklady Akad. Nauk SSSR
152, 1111 (1963).
[91] Cf. method for the preparation of :CHal2 by alkaline hydrolysis of HCHal3 [4-61.
Angew. Chem. internat. Edit.
/ Vol. 5 (1966) No. 12
and polymers containing CHz-CH=CH-CHz -GeHalz
units [88,89,921.
Trihalogenogermanes and their ether adducts react with
other conjugated dienes to form similar compounds [90.921.
The ether adducts (16) have been found usefd in many other
reactions as sources of carbene-like compounds [743899901.
In particular, hydrolysis of (16) (and of HGeHal3) leads to
GeO or Ge(0H)Z. Organomagnesium and organolithium
compounds cause the telomerization of germanium dihalides
or their alkylation (arylation) products that is characteristic
of carbenes and their analogues.
For example, the adducts (16) react with Grignard compounds
to the polymers (18).
2 RzO
( R' H al)
R' - (GeR$),- R'[74,89]
R=CzHz; R'= Alkyl or Aryl; Hal= CI, Br; Y = CI, Br, Alkyl,
or Aryl
The telomers (18) are formed also from GeIz and R'MgHal
or R'LiI74.891.
The "carbene-like" character of the trihalogenogermanes, and in particular of their ether adducts (16),is
shown by their strong reducing acticn towards inorganic
oxide salts and aromatic nitro compounds 1749931.
GeC12 is assumed to occur as an intermediate also in the
reactions of trichlorogermane ether adducts (16a) with
ethylene and acetylene [74,89,92J. Polymers containing
GeC12 groups in the main chain are obtained also by the
reaction of other olefins with HGeC13 in ether 1921.
Corresponding to the preparation of GeBr2 and GeI2,
germanium dichloride can be obtained from HGeC13 [941
> 33oc
n GeH4
+ 2(GeHh;
The reaction proceeds probably via diphenylgermanium.
Diphenylgermanium may occur as an intermediate in the
reaction of diphenyldichlorogermane with naphthalenesodium in dimethoxyethane [991.
'in (CH=CH-GeC12)"
[92] 0. M . Nefedov and S. P . Kolesnikov, Vysokomol. Soedin. 7 ,
1857 (1965).
[93] 0. M . Nefedov, S. P. Kolesnikov, and N . N . Machova, Izvest.
Akad. Nauk SSSR, Ser. chim. 1964, 2224; and literature cited
[94] C. W. Moulton and J. G. Miller, J. Amer. chem. SOC.78,
2702 (1956).
Angew. Chem. internat. Edit.
+ [:GeH2] +
Dialkyl- and diarylgermanium dihalides RzGeHal2
react with alkali metals in the same waj as RzSiHalz to
form linear and cyclic polymers (R2Ge)n. For example,
(C&)2GeC12 and sodium in boiling xylene give a
cyclotetramer (35 % yield) and a higher polymer (65
yield) 1991.
C12XGe- CH=CH-GeC13
X = H , C1
NaGeH3-k C6HSBr
(GeH& which is stable at room temperature, has also
been prepared by reduction of tetrachlorogermane with
LiAlH4 in ether 1981.
2 RzO.HGeC13
or its ether adductr74,891, but only in the polymeric
form. (GeCI& is a solid which decomposes at about
140 "C. (GeClz),? and the monomeric germanium dihalides and their ether adducts dissolve readily in hydrochloric acid to form the trihalogenogermanes [74,89,951.
Germanium dichloride, probably also in the polymeric
form, is formed when GeC14 vapor is passed over germanium powder at 350-430 "C 1951.
Monomeric GeCl2 in the form 2f its complex with dioxane, C4H802.GeC12 is formed when trichlorogermane
is mixed with dioxane[95a). This complex reacts with
1,3-dienes, alkynes, benzyl chloride and other compounds similarly to the stable germanium dihalides and
the ether complexes of trihalogermanes. GeF2 forms
the similar complex (C4HgO&.GeF2 ( x = 0.92-0.95)
with dioxane [851.
Chlorination of (GeClZ), leads to GeC14, hydrolysis to
GeO, and the action of H2S to GeS. Heating yields
subchlorides (Ge~C13)~
and (GeCl),, or even Ge and
GeC14 [74,951.
Unlike GeF2, GeBrz, and GeI2, compounds of bivalent
germanium with hydrogen or organic substituents are
unstable in the monomeric state. :GeHz and :GeR2
generally are liberated thermally or via organometallic
compounds. For example, pyrolysis of the germanium
hydrides Ge4Hlo and Ge~H12above 100°C leads to
germylene :GeH2, which then polymerizes [961. :GeH2
and (GeHZ), can be prepared also by reaction of bromobenzene with NaGeH3 in benzene below -33 "C[971.
NaGeH3 is obtained from GeH4 and sodium in liquid
VoI. 5 (1966)
No. 12
[95] L. M . Dennis and H . L. Hunter, J. Amer. chem. SOC.5 1 ,
1151 (1929).
[95a] S. P. Kolesnikow, W. 1. Schirjaew, and 0. M . Nefedov,
Izvest. Akad. Nauk SSSR, Ser. chim. 1966, 584.
[96] E. Amberger, Angew. Chem. 71, 372 (1959); cf. [1,5,15].
[97] S. N . GIarum and C. A . Kraus, J. Amer. chem. SOC.72,
5398 (1950).
[98] E. D . Macklen, J. chem. SOC. (London) 1959,1984;the yield
of GeH4 in this case was only 30y6,whereas almost quantitative
yields of CH4 and SiH4 are obtained under the same conditions
from CC14 and SiC14, respectively.
[99] W . P . Neumann and K . Kuhlein, Liebigs Ann. Chem. 683, 1
(1965); further literature cited there.
Finally, R2Ge: can be obtained by thermal depolymerization of (RzGe), 157-599661 and by pyrolysis of the
phenylacetylene-germacyclopentadieneadduct 1591.
Dialkyldichlorogermanes react similarly with alkali metals.
Thus reduction of (CH3)2GeCl2 with lithium in tetrahydrofuran leads to dodecamethylcyclohexagermane (19) and a
polymer (20) that is insoluble in the usual solvents [56-59,1001.
Under optimal conditions, the yields of (19) and (20) were
as high as 70-80%. Monomeric dimethylgermanium was
detected by the almost complete absence of low molecular
weight polygermanes when lithium was added to a large
excess of (CH3)2GeC12[581 and by the addition of (CH3)zGe:
to ethylene [56,58,59,661.
Diethylgermanium (CzH5)zGe: probably occurs as intermediate in the reaction of (CzH5)2GeC12 with lithium in
tetrahydrofuran, which leads mainly to insoluble polydiethylgermanium [(CzH5)2Ge], [58,591. Phenylgermanium chloride
C6H5(Cl)Ge: may be involved as intermediate in the reactions
of C6HsGeCl3 with alkali metals [1011.
Polymers of bivalent germanium can be prepared by
thermal or photochemical decomposition of polymeric
germanium-mercury compounds [991.
c) Tin Compounds
The halogen compounds of bivalent tin are obtained
when tin is dissolved in halohydric acids [1041. They are
stable in air.
+ 2 HHal
The difluoride is formed by the action of anhydrous
hydrogen fluoride on tin[ssl (8 hours at 200°C). Tin
diiodide can also be prepared from SnC12 and KI [1041.
The unsaturated (carbene-like) character of the tin dihalides is shown in many addition reactions that are also
characteristic of dihalogenocarbenes and their other
SnHalz+ 1/202 + OSnHal2
SnHal2+ Hal2
Neither (C6H&Ge: nor the polymers [(CsH5)2Ge]n
can be prepared by the action of CsHsLi, C6H5MgBr,
or (C6H5)3M on GeI2. It may nevertheless be assumed
that (C6Hs)zGe: is formed initially. Its formation is
indicated in particular by the production of small
quantities of triphenylgermane in the hydrolysis of
(C6H&GeLi, which was probably formed from
(C&)2Ge: and C&Li [l021.
+ H2
Hal = C1, Br, I
SnI2+ CH3I
4 hr
25 %
2 SnC12
+ 2: CHZ
+ 2 [C12Sn=CH2] --+
l/n(SnCI~CH2SnC12CH2SnCl~) [105a]
n-C5H5Fe(CO)zCl+ SnC12
[ X - C ~ H S F ~ ( C O ) ~SnHalp
[ X - C ~ H ~ N ~ C OSnC12
I Z --+ ClpSn[n-C5H5NiCO]2 [106b]
Diethyl- and di-n-butylgermanium is formed by the
action of mercury dialkyls R2Hg on GeI2 in ether [1033.
However, these compounds immediately change into
stable telomers.
[lo01 0. M . Nefedov, M . N. Manakov, and A . D . Petrov, Doklady Akad. Nauk SSSR 147, 1376 (1962).
[loll W. Metlesics and H . Zeiss, J. Amer. chern. SOC.82, 3321
(1960); further literature cited there.
[lo21 F. Glockling and K . A . Hooton, J. chem. SOC.(London)
1963,1849; cf. the reaction of the ether adducts (16) with organometallic compounds [74,89].
[lo31 G. Jacobs, C . R. hebd. Seances Acad. Sci. 238,1825 (1954).
Coz(CO)s+ SnHal2
%ZO"C; 15min
- ---
-+ Hal2Sn[Co(C0)4)2 [106b]
[lo41 G. Brauer: Handbuch der Prdparativen Arorganischen
Chernie. Enke, Stuttgart 1954.
[lo51 P. I'feifler, Ber. dtsch. chern. Ges. 44, 1269 (1911).
[105a] A . Ya. Yakubovich et al., Doklady Akad. Nauk SSSR 72,
69 (1950).
[lo61 P. Pfeiffer and I. Heller, Ber. dtsch. chern. Ges. 37, 4618
[106a] F. Bonati and G. Wilkinson, J. chern. SOC.(London) 1964,
[106b] D . J. Patmore and W. A . G. Graham, Inorganic Chem. 5 ,
1405 (1966).
Angew. Chem. internat. Edit.
1 Vol. 5
No. 12
SnC12 and SnBr2 can displace mercury from its dialkyl
and in particular from its diary1 derivatives 11071:
R 2 H g t SnHal2
+ R2SnHal2+
SnC12 and its solutions in hydrochloric acid, as well as
SnCl2-ether adducis, have a strong reducing action
towards inorganic salts, aromatic nitro compounds,
and azides [93,107,1081.
Preparation and properties of organic derivatives of bivalent tin have been reported by Ingham et d.[lo91 and
by Neumann [1101. Dialkyl- and diaryltin, like their
silicon and germanium analogues, are stable only in the
polymeric form L1101, although monomeric tin dialkyls
and in particular monomeric diphenyltin were formerly
thought to be fairly stable[llll. The polymeric nature of
dibutyltin and diphenyltin has been deduced from the
Mossbauer spectra [1121.
The best methods for the preparation of cyclopolymers of
diphenyltin [(C6H5)2SnIn are the catalytic decomposition of
diphenyltin hydride in the presence of amines or amides [110,
1131 and the action of naphthalenesodium on diphenyldichlorostannane [1131.
with SnC12 in tetrahydrofuran leads to polymers (22) with
= 13-14, which are probably also cyclic~1131.
The polymer
(22) is formed also during the thermal dehydrobromination
of diphenylbromostannane [1151.
(C6H5)2SnHBr + [(CsHs)rSn:I + I/n[(C6H5)2Sn]n
Probably the cyclopolymers (22) readily undergo
complete depolymerization. Their chemical properties
show them to be typical carbene analogues. In particular, they are readily oxidized by atmospheric oxygen
or hydrogen peroxide to (GH5)2SnO. They add sulfur
and halogens to form (C6H&SnS and (C6H&SnHal2,
respectively, and reduce A g N 0 3 and HgC12 to the
metals [109,113,1161. A particularly characteristic property of diphenyltin is its ability to undergo insertion
into the S-S bond of dibenzyl disulfide 11161:
Like carbenes and other carbene analogues diphenyltin
forms an easily oxidized complex ( C & ) ~ S ~ . P ( C ~ H S ) ~
with triphenylphosphine [116al:
-% R2SnO
t OPR,
R = CsH5
Cyclohexamers of di-p-tolyl-, di-p-ethoxyphenyl-, di-p-biphenylyltin, and di-a- and di-@-naphthyltinhave been obtained
in high yields by catalytic decomposition of the corresponding diaryltin dihydrides [1141.
The cyclohexamer (21) is formed also by the action of alka!i
metals, zinc, or magnesium on (C6H5)zSnCIz in tetrahydrofuran (yield 5-25 %) [1131. However, thereaction of C6HsMgBr
[lo71 A. N. Nesmejanow and K . A . KoreschkGw, Ber. dtsch. chem.
Ges. 63, 2496 (1930).
11081 0. Dimroth et al., Ber. dtsch. chem. Ges. 40, 2376 (1907);
43, 2757 (1910); 50, 1534 (1917).
[lo91 R . K . lngham, S. D . Rosenberg, and H . Gilman, Chem.
Reviews 60, 459 (1960).
[ l l O J W. P . Neumann, Angew. Chem. 75, 225 (1963); Angew.
Chem. internat. Edit. 2, 165 (1963).
Diphenyltin adds to compounds containing CC double
bonds, e.g. tetrafluoroethylene [1171.
+ X/n[(CgH5)2Sn] *
The tendency of polymeric diphenyltin to depolymerize
and the biradical character of (C6H&Sn: are confirmed
by the addition of free radicals [116,1191.
C&,. + CH3COO.
[1111 See, e.g., E. Krause and R . Becker, Ber. dtsch. chem. Ges.
53, 173 (1920); R . F. Chambers and P . C . Scherer, J. Amer. chem.
SOC.48, 1054 (1926).
[1121 W. I. Goldansky, W. Ya. Rochev, and W. W . Khrapov,
Doklady Akad. Nauk SSSR 156, 909 (1964).
[113] W . P . Neumann and K . Konig, Liebigs Ann. Chem. 677, 1
(1964); furthcr literature cited there.
[I141 W. P. Neumann and K . Konig, Liebigs Ann. Chem. 677, 12
Angew. Chem. internat. Edit.
/ Vol. 5 (1966) No. 12
[1151 G. Fritz and H . Scherer, Z. anorg. allg. Chem. 338,l (1965).
[116] H . G. Kuivila and E. R . Jakusik, J. org. Chemistry 26, 1430
[116a] H . Schumann, H. KopA and M . Schmidt, Z . Naturforsch.
196, 168 (1964); cf. [81,82].
[117] A . A . A . Beg and H . C . Clark, Chem. and Ind. 1962, 140.
[118] G . Wittig, F. I. Meyer, and G . Lange, Liebigs Ann. Chem.
571, 167 (1951).
103 1
Dialkyltin polymers are prepared like polymeric diaryltin,
e.g. by reaction of alkylmagnesium halides or alkyl-lithium
with tin dihalides I1099 110,1201 or with the ether adducts
2R20.HSnC13 [*91, by reaction of dialkyltin dihalides with
alkali metals or organic bases [1161. Moreover, the formation
of the cyclotetramer (23) has been observed during the reaction of excess of t-butylmagnesium chloride on t-butyltin
chloride in boiling tetrahydrofuran [1211,
+ 1/4[(t-C4H9)~Sn]4
The most suitable method for the preparation of dialkyltins is the catalytic or thermal dehydrogenation of the
dialkyltin dihydrides; the degree of polymerization of
the final product (R2Sn)n in this case is maidy determined by the catalyst [110,1201.
In addition to the tin dialkyls and diaryls, many other
organic and inorganic derivatives of bivalent tin have
been prepared, mostly from tin dihalides, e.g. :
ZSnBr;?+ 4NaOCH3 + 2Sn(OCH&
3 B2Ha
-2 HB(OCH3)z
(n-CqH9)~SnHz -(CH3)2C0+
100" c
(or -+)
[(n-C4H&Sn: ]
d) Lead Compounds
The preparation and decomposition of the dialkyltin
dihydrides (and diaryltin dihydrides) can be carried out
in a single process :
+ 2(C2H5)3SnH
__ +
4-1 hr
Ethyltin bromide can be prepared similarly from
C2HsSnH2Br, the product again being polymeric [*151.
Lead dihalides should also exhibit properties of carbenes,
but these should be much less pronounced than those
of tin dihalides. For example, whereas chlorine adds
irreversibly to SnC12 with formation of SnC14, PbC14
prepared similarly explodes spontaneously [1041.
Organic derivatives of bivalent lead probably are formed
in the reaction of Pb(n) salts with organometallic
The chemical properties of the tin dialkyls closely
resemble those of the polymeric tin diaryls.
PbClz+ 2ArMgBr + ArzPb+ MgC12f MgBrz
The compounds R2Pb formed under these conditions
cannot generally be isolated, even as polymers, since
they readily react further.
Dialkyltin also readily inserts into C-Hal,
Sn-H, and apparently also Sn-Cl bonds.
[119] G. A. Rasuvaev and E. I. Fedotova,
obSE. Chim. 21, 1118
[120] W. P. Neumann and J. Pedain, Liebigs Ann. Chem. 672,34
(1964); further literature cited there.
[121] W. V. Farrar and H. A . Skinner, J. organometal. Chem. I,
434 (1964); cf. [70].
[122] H. G. Kuivila et al., J . Amer. chem. SOC.83, 1246 (1961);
85, 1010 (1963).
11231 N. S. Vyasankin, G. A . Rasuvaev, and S. P. Korneva, 2.
obSE. Chim. 34, 2787 (1964).
[124] A. N . Nesmeyanov, K . A. Kocheshkov, and W. P. Puzireva,
2. obSE. Chim. 7, 118 (1937).
+ R4Pb+ Pb
2R3Pb+ Pb etc.
[125] W. T. Bischkov and N . S. Vyasankin, 2. obSE. Chim. 35,
687 (1965).
[126] C. A . Kraus and W . N . Greer, J. Amer. chem. SOC.47,2568
[127] E. Amberger and M.-R. Kula, Chem. Ber. 96, 2556, 2562,
(1963); further literature cited there.
[128] K . V. Vijayarahavan, J. Indian chem. SOC.22, 227 (1945).
[129] E. 0.Fischer and H. Grubert, Z. anorg. allg. Chem. 286,
237 (1956).
[130] E. Krause and G. G. Reissaus, Ber. dtsch. chem. Ges. 55,
888 (1922).
[131] E. Bindschadler and H. Gilman, Proc. Iowa Acad. Sci. 48,
273 (1941); Chem. Abstr. 36, 1595 (1942).
[132] L. C. Willemsens and G. J. M . van der Kerk, J . organometal.
Chem. 2, 271 (1964); further literature cited there.
Angew. Chem. internat. Edit.
1 Vol. 5 (1966) / No. I2
Reactions of PbClz with organometallic compounds are
used to prepare organic derivatives of quadrivalent
lead [1331, e.g. :
( 2 5 ~
R = H, CH3, CzH5, C6H5; R'= H, p-CH3, p-CH30, P-Cl, 0- and
p-NOz, o - N ~ .
4. Carbene Analogues with Elements of Group
a) Nitrogen Compounds
Lwowski et at. [138bl examined the stereospecificity of
the addition of ethoxycarbonylimene to olefins.
Phenylimene can insert into the A1-C bondr1391. Like
the alkoxycarbonylimenes, it has a dehydrogenating
and decarbonylating action on alcohols and aldehydes [140,1411. An unusual reaction is that of the azide
(26) with norbornadiene, which formally is an insertion
of the phenylsulfonylimene into a C-C bond 11421.
The compounds of univalent nitrogen, :NR or .NR,
which are known as imenes, nitrenes, or azenes, have
been studied more fully than any other carbene analogues 1134, 1351. Imenes and carbenes, which are prepared from azides and diazo compounds, respectivelq,
were comvared bv Kirmse 11361.
recent publications that were not mentioned
in the reviews[134-1361, we shall select only a few.
Studies on intermolecular and intramolecular insertions
of imenes into aliphatic C-H bonds were concerned
with the direction and selectivities of these reactions,
the relative reactivities of various imenes, and the
optical activity of the resulting heterocyclic compounds,
e.g. (24) and (25) [137,1381.
The photolysis of phew1 azide in diethylamine leads to
ring enlargement with the formation of 2-diethylamino3H-azepine [1424.
Another interesting reaction is that of ethoxycarbonylimene (27) with aliphatic nitriles, which leads to substituted 1,3,4-oxadiazoles (28) [1431.
(28), 14-7 370
R = CH3, iso-C3H,, C2H50-CH2-CH2,
The reaction of ethoxycarbonylimene (27) with thiophene, pyrrole, and furan 11441 leads to the heterocycles
(29) to (31).
R = H , CH3
(29), 18-2170
The intramolecular cyclization of imene (25a), formed
by thermal decomposition of 3-azido-4-benzylideneamino-s-triazoles, gives triazolotriazoles (25b) [138al:
[133] L. C . WilIemsens and G. J. M . van der Kerk, J. organometal.
Chem. 2, 260 (1964); see also [128,130-1321; E. C . Juenge and
S . E. Cook, J. Amer. chem. SOC.81, 3578 (1959).
[134] L. Horner and A . Christmann, Angew. Chem. 75, 707
(1963); Angew. Chem. internat. Edit. 2, 599 (1963).
[135] R . A. Abramovitch and B. A . Davis, Chem. Reviews 64,149
[136] W. Kirmse, Angew. Chem. 71, 537 (1959).
[137] M . F. Sloan, T. J. Prosser, N . R . Newburg, and D . S. Breslow, Tetrahedron Letters 1964, 2945; T . J. Prosser et al., ibid.
1964, 2483; J, H . Hall, J. W. Hill, and Hu-chu Tsai, ibid. 1965,
2211; W . Lwowski and T . J. Maricich, J. Amer. chem. SOC. 86,
3164 (1964).
[138] G. Smolinsky and B. 1. Feuer, J. Amer. chem. SOC.86, 3085
[138a] H. H . Takimoto, G . C. Denault, and S. Hotta, J. heterocyclic Chem. 3, 119 (1966).
Angew. Chem. internat. Edit.
Vol. 5 (1966)
No. 12
[138b] W. Lwowskiet al., J. Amer.chem. SOC.87;5490,5491(1965).
[139] K . Hoegerle and P. E. Butler, Chem. and Ind. 1964, 933.
[140] R . Puttner and K . Hafner, Tetrahedron Letters 1964, 3119.
[141] T. J. Prosser, A . F. Marcantonio, and D . S . Breslow, Tetrahedron Letters 1964, 2479.
[142] J. E. Franz and C. Osuch, Chem. and Ind. 1964, 2058.
[142a] W. von E. Doering and R . A . Odum, Tetrahedron 22, 81
[143] W . Lwowski et al., Tetrahedron Letters 1964, 2491.
[144] K . Hafner and W. Kaiser, Tetrahedron Letters 1964, 2185.
The 1,3-dipolar cycloaddition of alkoxycarbonylimenes
to C r C triple bonds leads usually to the corresponding
oxazoles [1444. However, formation of a cyclopropene
derivative was recently observed [144bJ.
- NZ
The electron spin resonance spectra of various imenes
have been studied [146-146bJ and the bond energies, the
lifetimes, and the electronic states of the alkoxycarbonylimenes, which were prepared by photolysis of the alkyl
azidoformates in the gas phase, have been determined [1471.
b) Phosphorus Compounds
I1 - C - CH3
CH3- C
H3c&= N - C OOC H3
Reference should also be made to the synthesis of Ncyanoazepines (32) from cyanoimene and aromatic
compounds [1451.
The most intensively studied of the compounds of univalent phosphorus is phenylphosphorus (33), which can
be prepared by dechlorination of phenyldichlorophosphine, by dehydrogenation of phenylphosphine, or by
cleavage of the corresponding cyclopolymer, and which
can be readily detected as the disulfide adduct 11481.
132b), 76%
Combination reactions of the imene :NH, generated in
the flash photolysis of isocyanic acid (HNCO), were
discussed by Buck [145al. Aromatic imenes formed from
azides isomerize intramolecularly to nitriles [145b, cl.
Disulfides react similarly with diphenyltin [1161 and
methylene 11491.
Phenylphosphorus (33) prepared from C6HsPC12 and
zinc also adds to benzil[14*1.
Organic derivatives of univalent phosphorus, RP:, are
assumed to occur as intermediates in the reactions of
aryl- or alkyldichlorophosphines with magnesium or
lithium in tetrahydrofuran, which lead to cyclic or
linear polymers (34) 11501:
M g
R = Alkyl or Aryl; n = 4 o r 5
The reaction of organodibromophosphines with magnesium in ether/benzene follows a similar course [1511
(R = CH3, C2H5, C6H5; n = 5 or 6).
[144a] R . Huisgen and HI Blaschke, Chem. Ber. 98, 2985 (1965);
further literature cited there. On the mechanism of 1,3-dipolar
cycloaddition see R. Huisgen, R. Sustmann, and K . Bunge, Tetrahedron Letters 1966, 3603 ; further literature cited there.
[144b] J. Meinwald and D . H . Aue, J. Amer. chem. SOC. 88,
2849 (1966).
[145] F. D. Marsh and H . E. Simons, J. Amer. chem. SOC.87,
3529 (1965); cf. the analogous rcaction of the imene (27) [K. HaF
ner and C . Konig, Angew. Chem. 75, 89 (1963); Angew. Chem.
internat. Edit. 2, 96 (1963)J.
[145a] R. A. Back, J. chem. Physics 40, 3493 (1964).
[145b] K. Nakagawa and H . Onoue, Chem. Commun. 1965, 396,
and literature cited there.
[145c] J. D. Hobson and J. R. Malpass, Chem. Commun. 1966,
[146] E. Wassermann, G. Smolinsky, and W. A. Yager, J. Amer.
chem. SOC. 86, 3166 (1964).
[146a] R. M . Moriarty, M . Rahman, and G. J. King, J. Amer.
chem. SOC.88, 842 (1966).
[146b] J. A. R. Coope et al., J. chem. Phys. 42, 54 (1965).
[147] D . W . Cornell, R. S. Berry, and W . Lwowski, J. Amer.
chem. SOC.87, 3626 (1965).
[148] U. Schmidt and Ch. Osferroht, Angew. Chem. 77, 455
(1965); Angew. Chem. internat. Edit. 4, 437 (1965).
11491 A. Schonberg, 0. Srhiitr, and J . Peter, Ber. dtsch. chem.
Ges. 62, 440 (1929).
[150] W. A. Henderson, M . Epstein, and F. S . Seichter, J. Arner.
chem. SOC.85, 2462 (1963); and literature cited there. Cf. [63,65,
66,981. For preparation, properties, reactions, and structures of
cyclopolyphosphines see also A. H. Cowley, Chem. Reviews 65,
617 (1965).
11511 W . Kuchen and W. Griinewald, Chem. Ber. 98, 480 (1965).
Concerning the ring sizes of cyclopolyphosphines formed in
these ways see A. H. Cowley and R. P. Pinnell, Inorganic Chem.
5, 1459 (1966), and literature cited there.
Angew. Chem. internat. Edit.1 Vol. 5 (1966) No. I 2
RP: may occur as intermediate in other reactions used
for the preparation of polymers.
-2 HCl
stable arylarsenes ArAs: are probably formed in the
reduction of the arylarsonic acids, and are subsequently
stabilized by cyclopolymerization 11561.
[ArAs:] + 1/6(ArAs)6
Ar = C6H5, p - and m-CH3-CsH4
Like the diorganotin dihydrides, phenylstibine, which
is prepared at -196" to -6O"C, decomposes with
evolution of hydrogen, giving first monomeric and then
polymeric phenylantimony (38) [1571:
l / n(C~iH5Sb)n
Derivatives of univalent phosphorus are formed in the pyrolytic or catalytic cleavage of some phosphines or diphosphines [1531.
Similarly, polymeric ( c ~ H 5 B i ) (39)
is formed via
C6HsBi: from C6HsBiH2, which is prepared at -110 to
-70 "C [1571.
Oxidation of the polymer (38) by atmospheric oxygen
leads to a polymer containing -(C6H5)Sb(=O)- units.
Unlike (38), polymeric phenylbismuth (39) behaves
towards oxygen and halogens in the same way as the
other carbene analogues and their polymers:
The polymers (CF3P),, like the other polymeric carbene
analogues, readily add halogenes to form CF3-PHal2; they
are oxidized by oxygen to (CF3-P02), [1531. The organodifluorophosphines RPF2 lose a molecule of fluorine at
20-40 "C to form the carbene analogues, which are then
converted into the cyclopolymers [1541. Butylphosphorus (35),
which'can add to alkynes, is formed by the catalytic cleavage
of tributylphosphine 1691:
136Iz 4%
n C6H5Bi0
(c6H~Bi)n nBr2 -+ n C6HsBiBr2
5. Elements of Group VI as Carbene Analogues
Oxygen, sulfur, selenium, and tellurium atoms are
carbene analogues on the basis of their electronic structure and their chemical properties. They undergo many
carbene reactions, such as dimerization and polymerization, addition to double and triple bonds, and insertion
into single bonds. The addition of atoms of group VI
elements in the singlet state to the C=C double bond is
strictly electrophilic, as in the case of singlet carbenes
(Table 1).The reaction leads stereospecifically to threemembered rings.
Table I . Reaction of carbenes and carbene analogues with olefins. The
data are the relative rates (kllkz) of addition of various reagents to
Finally, :PI could occur as intermediate in the formation of
the heterocycles (36) and (37) from tetrafluoroethylene, red
phosphorus, and iodine [1551.
(37), 27%
c) Arsenic, Antimony, and Bismuth Compounds
The compounds of univalent arsenic, antimony, and
bismuth and their polymers have been studied even less
than the analogous phosphorus compounds. The un11521 H. Fritrsche, U. Hasserodt, and F. Korte, Angew. Chem.
75, 1205 (1963); Angew. Chem. internat. Edit. 3, 64 (1964).
[153] W. Muhler and A . B. Burg, J . Amer. chern. Soc. 80, 6161
[154] W. N . Kulakova, Yu. M . Zinovyev, and L. Z . Soborovsky,
2. obSt. Chim. 29, 3957 (1959).
[1551 C . G. Krespan and C. M . Langkammerer, J. org. Chemistry
27, 3584 (1962).
Angew. Chem. internat. Edit. 1 Vol. 5 (1966) J No. 12
trans-CHs-CH= CH-C
[156] G. M . Badger, R . J. Drewer, and G. E. Lewis, Austral. J .
Chem. 16, 285 (1963); further literature cited there.
[157] E. Wiberg and K . Miidritzer, Z . Naturforsch. IZb, 128, 131
[158] W. von E . Doering and W. A . Henderson, J. Arner. chern.
SOC.80, 5274 (1958).
However, most of the reactions of molecular oxygen, sulfur,
and selenium in which individual atoms could formally
participate are not associated with preliminary dissociation
or depolymerization of the molecules. Therefore most of
these reactions will not be discussed.
tion of small amounts of acetaldehyde alongside formaldehyde as main product is explained by the insertion
of atomic oxygen in C-H bonds during its reaction with
ethylene 11661.
a) Oxygen
+ 0
HzC=CH2 + 0
Atomic oxygen is usually produced by the passage of a
high-voltage discharge through water v a p x or molecular oxygen or by photolysis of nitrous oxide or nitrogen dioxide L16031631. Atomic oxygen, which is formed
on UV irradiation ( I = 2450-3700 A) of N20 and N O 2 ,
and which is in the ground triplet state (3P), reacts as a
triplet carbene with olefins and dienes, forming epoxides,
aldehydes, or ketones [164,1651.
+ 0
+ Hz
The reactioiis of oxygen and of sulfur with phosphines,
carbenes, other carbene analogues, borontrialkyls etc.
are very similar to the corresponding reactions of carbenes. However, the participation of atomic oxygen or
sulfur in these reactions is very doubtful.
+ [O] ---+ R3PO
+ [O] + R2CO
R2Sn:+ [O] --+ R2SnO
However, when nitrogen dioxide is irradiated with light
of wavelength 2288 A, an excited oxygen atom (ID) is
obtained, which can add to olefins in one step like a
singlet carbene. This is seen from the greatly increased
yield of epoxide L1651.
Like that of the singlet carbenes the addition of excited
oxygen O(1D) to olefins is stereospecific. However, the
stereospecificity is somewhat relaxed by the transition
O(1D) --t O(3P) [1651. The reaction of atomic oxygen with
lower olefins generally leads to an aldehyde and a
car bene.
H2CeCH2-t 0
CH2O+ :CH2
F2C=CF2+ O(3P) + CF20+ :CF2
,c=c: +
b) Sulfur
Atomic sulfur in solution occurs during the photochemical formation of isonitriles from isothiocyanates
(A = 254 mp), and can be detected like the carbenes by
addition to cyclohexene [1481.
Atomic oxygen can also attack aliphatic and aromatic
C-H and even C-C single bonds [166,1681. The forma[159] P. S. Skelland A. Y . Garner, J. Amer. chem. SOC.78, 5430
[160] R. J. CvetanoviC, Adv. Photochem. I, 115 (1963); further
literature cited there.
[161] P. 0. Strausz and H. E. Gunning, J. Amer. chem. SOC.84,
4080 (1962).
[162] A. B. Callear and W. J. R. Tyerman, Proc. chem. SOC.
(London) 1964, 296.
11631 F. Kaufman, Progr. Reaction Kinetics I, 1 (1951); further
literature cited there.
[164] S. Sato and R. J. CevetanoviC, Canad. J. Chem. 36, 279,
970 (1958); R. J. CvetanoviC, ibid. 36, 623 (1958); R. J. CvetanoviC
and L. C. Doyle, ibid. 38, 2187 (1960).
[165] S.Satoand R.J. CvetanoviC,Canad.J.Chem.36,1668(1958).
[166] L. I. Avramenko and R. W. Kolesnikova: The Problem of
Chemical Kinetics, Catalysis, and Reactivity. Academy of
Sciences, Moscow 1955, p. 7 ; further literature cited there;
Advances in Photochemistry 2, 25 (1964).
[167] D. Saunders and J. Heicklen, J. Amer. chem. SOC.87, 2088
[168] L. I. Avramenko, R. W. Kolesnikova, and G. I. Savinova,
Izvest. Akad. Nauk SSSR, Ser. chim. 1965, 28.
+ [O] --+ RzBOR
The Prileshayev reaction (oxidation of alkenes and
alkynes by peracids or hydrogen peroxide 11711) formally
resembles the reactions of carbenes.
R , R’, R2 and R3 = H , A l k y l , o r A l k e n y l
Atomic sulfur is formed in the excited singlet state
S(1D) in the gas phase occurs during the photolysis
(A = 2290-2555 A) of carbonyl sulfide at 25 “C[161,172,
In the photolysis of COS in a n inert gas at high pressures, the
conversion of the initially formed S(1D) into the ground
triplet state S(3P) is increased by collisions with the gas molecules~l73J.The singlet sulfur can insert into C-H bonds of
alkanes, cycloalkanes, and alkenes, whereas the triplet sulfur
cannot; on the other hand, both types can add to C=C
double bonds [16l9172-172bJ.
[169] E. Miiller: Neuere Anscbauungen der organischen Chemie.
Springer, Berlin 1957.
[170] J. R. Johnson and M. G. van Campen, J. Amer. chem. SOC.
60, 121 (1938).
[171] See, e.g., N . Prileschajyev, z. russ. fiziko-chim. ObSEestva
42, 1387 (1910); H. H. Schlubach and V. Franren, Liebigs Ann.
Chem. 577, 60 (1952); W. N. Sapunov and N. N. Lebedev,
organ. Chim. 2, 225 (1966), and further literature cited there.
11721 A. R. Knight, 0. P. Strausz, et al., J. Amer. chem. SOC.85,
2349 (1963); 86, 4243 (1964); 87, 1443 (1965).
[172a] K. S. Sidhu, E. M. Lown, 0. P. Strausz, and H. E. Gunning, J. Amer. chem. SOC.88, 254 (1966).
[172b] On reactions of sulfur atoms see also H. E. Gunning,
Trans. Roy. SOC.Canada, Sec. 1-3, 2, 293 (1964).
Angew. Chem. internat. Edit,
/ Vol. 5
No. 12
of an inert gas, e.g. nitrogen, the initially formed “hot”
selenium atoms (lifetime ca. 10-4 sec) are deactivated
and subsequently dimerize to form Se2.
Like oxygen and sulfur, selenium and tellurium insert
into the Sn-Li [1781 and even Sn-C [I791 bonds; however, the reaction probably does not involve preliminary
depolymerization of the Sex and Tex molecules. Sex and
Te, also react with tetrafluoroethylene ”551, olefins, and
acetylene [1801.
As was recently shown [172a1 episulfides formed from
cis- and trans-Zbutene retain the geometry of the parent
olefin (retention > 87 and > 98 %, respectively) not
only with singlet but with triplet-state sulfur as well.
The addition of sulfur atoms to 1,3-butadiene gives at
least 91 % of vinylthiirane, with thiophene ( < 9
second major product 1172al.
Atomic sulfur is thought to be involved in the reactions
of hexafluoropropylene and tetrafluoroethylene with
sulfur vapor at 400-500 “C [174,174al:
Atomic sulfur probably is formed when diethyl tetrasulfide is heated [1751.
R = H , CH3
6. Transition Metal Compounds with
Carbene-like Properties
No carbene-like properties can be expected of free
transition metals, in which the d levels with lower principal quantum numbers than those of the s and p
valence electrons are not filled. However, some derivatives of these metals are formed by filling of the d levels
to form complexes or “sandwich” structures. Such
complexes could formally be expected to include
carbene analogues. For example, the platinum complex
[(C6H5)$]2PtCl is converted by hydrazine or other
reducing agents into a carbene analogue (40), which
can add to alkynes to form the compounds (41) [1811.
Compound (40) also forms unstable adducts with
olefins [1811.
T h e photolysis of derivatives of cyclopentadienylmanganese
tricarbonyl with subsequent addition of tolan can also b e
formulated a s proceeding via a carbene analogue (42),
though it probably involves displacement of CO by tolan “821.
Molecular (polymeric) sulfur can undergo insertion
into the Sn-Li bond to form the group SnSLi [1761. At
it adds to olefins, dienes, and alkynes to
form hetero chains and heterocycles [1771. However, it is
unlikely that atomic sulfur is involved in these reactions.
T h e formation of t h e titanocene derivative could also be
formulated a s involving a carbene analogue 11831 :
c ) Selenium and Tellurium
Atomic selenium in the excited state is formed during
isothermal flash photolysis of carbon diselenide vapor,
and adds electrophilically to olefins [1621. In the presence
[173] Cf. the singlet-triplet transition of methylene in the gas
phase [5,6].
[174] K . V. Martin, J. chem. SOC.(London) 1964, 2944.
[174a] W . R. Brasen et al., J. org. Chemistry 30, 4188 (1965).
[1751 S. 0. Jones and E. E. Reid, J. Amer. chem. SOC.60, 2452
[1761 H . Schumann, K . F. Thom, and M . Schmidt, J. organornetal.
Chem. 2, 97 (1964).
[I771 H. E. Westlake ec al., J . Amer. chern. SOC.68, 748 (1946);
further literature cited there; B. A . Arburov and E. G. Kataev,
Doklady Akad. Nauk SSSR 96, 983 (1954); J . B. Peel and P . L.
Robinson, J . chern. SOC.(London) 1928, 2068.
Angew. Chem. intertiat. Edit.
Vol. 5 (1966) 1 No. 12
[178] H . Schumann, K . F. Thom, and M . Schmidt, J. organometal. Chem. 2, 361 (1964).
[179] M . Schmidt and H . Schumann, Chem. Ber. 96, 780 (1963).
[180] W . E. Garwood, F. M . Seger, and A . N. Sachanen, US-Pat.
2500164 and 2500167 (14 March, 1950); Chem. Abstr. 44, 4670
( I 950).
[181] J . Chat?, G . A . Rowe, and A . A . Williams, Proc. chem. SOC.
(London) 1957, 208.
11821 W . Strohmeier, H . Laporte, and D . von Hobe, Chem. Ber.
95, 455 (1962).
[I831 M . E. Volpin, W. A . Dubovizky, 0 . W . Nogina, and D . N .
Kursanuv, Doklady Akad. Nauk SSSR 151, 1100 (1963).
7. Carbene-like Properties of other Compounds
Some elements of the third and subsequent periods
(phosphorus, antimony, sulfur, selenium, and others)
can form five covalent bonds, i.e. can possess a stable
decet of electrons.
Accordingly, many compounds of these elements exhibit carbene-like properties, even when the atom still
possesses eight valence electrons. In particular, phosphoranes and phosphine oxides with covalent structures may be regarded as adducts of such carbene
analogues with carbenes or oxygen [1691.
R3P+ :CX2
+ R3P=CX2
R3P+ 1/202
The reaction of phosphorus trihalides with compounds
containing conjugated double bonds [1841 appears to
suggest carbene-like properties in the former:
: PHal ,
H a l = C1, B r
[184] U. Hasserodt, K. Hunger, and F. Korte, Tetrahedron 19,
1563 (1963); B. A . Arbuzov and A . 0 . Vizel, Doklady Akad.
Nauk SSSR 158, 1105 (1964), and literature cited there. Cf. the
1,4-addition of other carbene analogues and carbenes to 1,3dienes [73,74,87].
Sulfur and selenium dioxides form similar products
with conjugated dienes 11851. S O 2 and SeO2 add particularly readily to 2,3-di t-butyl-l,3-butadiene.
1,3-Dienes add easily not only PHal3, but also alkyland aryldichlorophosphines RPC12. However, the adducts (43) are ionic and can be reduced smoothly with
magnesium in T H F to derivatives of three-covalent
phosphorus (44) [1861.
+ RPClz
These results shows that compounds having carbenelike properties do not necessarily have the electronic
arrangement of the carbenes. The central atoms of
these compounds have no free p orbitals, but use vacant
d orbitals to form the decet of electrons at the expense
of pd hybridization.
We thank Dr. H . Reimlinger and Dr. E. H . Braye for
suggesting corrections to the manirscript.
Received: December loth, 1965
[A 546 IE]
German version: Angew. Chem 78, 1039 (1966)
Translated by Express Translation Service, London
[185] H. J. Backer and J. Strafing, Recueil Trav. chim. Pays-Bas
53, 525, 1113 (1934); 54, 170 (1935).
Thermal a n d Photochemical Formation of
Phospholenes and Tetrahydrophosphorins from
Cyclophosphines and Dienes [11
By Prof. Ulrich Schmidt and I. Boie
follow from their compositions, molecular weights (determined mass-spectrometrically), and NMR spectra.
The tetrahydrophosphorins react rapidly with alkylating
agents to give monophosphoniurn salts and with sulfur to
give P,P'-bissulfides.
Chemisches Laboratorium, Universitat Freiburg (Germany)
We have previously inferred the formation of phosphinidene
(R-P:), o n heating and irradiation of cyclophosphines
(R-P)5, from reactions leading to insertion into disulfide
bonds 121, formation of 1,l'-spirobi(phosphadioxo1e) [21, and
exchange of ring members of cyclopolyphosphines 131. We
have now observed addition of fragments formed thermally
and photochemically from cyclophosphines to dienes.
Cyclophosphines were heated with dienes for 20 hr at 150 to
180 "C. On subsequent distillation a mixture of a phospholene
( I ) and a tetrahydro-1,2-diphosphorin(2) was obtained in a
total yield of 40 to 60 %. These products were separated by
fractional distillation. 1,2,3,6-Tetrahydro-l,2-diphosphorins
(2) can be isolated in better yield and without simultaneous
formation of phospholenes ( I ) by irradiation of the cyclophosphine-diene mixture with a high-pressure mercury vapor
1 zi: 1
Method and
1 I
M.P. ("C) of
derivatives [a]
Phospholenes ( I )
Heat, 10
Heat, 23
B, 189
B; 183.5
B, 219-221
Heat, 22
hv, 19
Heat, 40
hv, 53
Heat, 25
D , 176-177
D, 94
D, 193
D, 178-179
[a] B = 1-Benzylphospholenium bromide; D
1,2-diphosphorin 1,2-bissulfide.
[b] D o u b l e t r = 9 . 1 5 p p m ( 3 H ) ; J = 3.3Hz;sinplet.r;8.30ppm(6H);
multiplet T = 7.12 - ca. 8.55 ppm (4 H).
[c] Triplet 7 = 9.02 ppm (6 H); J = 18.6 Hz; singlet r =8.20 ppm (6 H);
multiplet J = 7.37-8.47 ppm (4 H).
(Neat liquids, TMS as internal standard).
[Z 344 IEI
Received: August lst, 1966
German version: Anpew. Chem. 78, 1061 (1966)
Publication delayed at the authors' request
The structures of the phospholenes and tetrahydro-1,2-diphosphorins (the latter are derivatives of a new ring system)
[l] Part 3 of Phosphinidenes. - Part 2: ref. [3].
[2] U. Schmidt and Ch. Osterroht, Angew. Chem. 77, 455 (1965);
Angew. Chem. internat. Edit. 4, 437 (1965).
[3]U.Schmidt, R. Schroer, and H . Achenbach, Angew. Chem. 78,
307 (1966); Angew. Chem. internat. Edit. 5, 316 (1966).
Angew. Chem. internat. Edit.
VoI. 5 (1966) J No. 12
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inorganic, organometallic, carbene, organiz, analogues
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