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Organometallic and Hydrogen Compounds of Some Transition Metals.

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R2
~
~
oil
87-90 [a]
136- 138
118-120
153- I56
115-117
98-100
94-96
79-81
118 (decomp.)
CO-(CH2)z-CO
o-CO-C6H4--CO
CO-(CHz)z-CO
o-CO-cbH4-cO
CO-(CH2)2--CO
CO-(CHz)2--CO
CO-(CHzf2-CO
CO-(CH2)2-CO
0-CO -CbH4- CO
[a1 M.P. of crude product, [bl c
[cl c = 2 in isopropyl alcohol.
+
(2)
~
1
-
=
75
92
64
80
75-78
46
65
71
70
73
~ R ~ N - oO
-, c : ~ ~ ~
When warmed (95 "C) for 2 h with amino acids in dioxanel
0.5 M NaZCO3 solution (2:1), these products afford, as was
shown by Frankel and co-workers [31 for (Saj and (Sc), alkoxycarbonylamino acids which are obtained in high yield by
evaporation of the solution in a vacuum, adjustment of the
pH to 3, extraction with ethyl acetate, and evaporation of
the solvent. (Sdj reacts in the same manner. BOC-amino
acids, which are of particular preparative importance, are
thus obtained more conveniently than by way of the BOChydrazide.
[Z 497 IE]
Received: March 28th and April 21st, 1967
German version: Angew. Chem. 79, 532 (1967)
..
-
..
~
-25
Icl[2]
1 in dimethylformamide,
0
+2.5' [b]
+ 20.4 [b]
[ * ] Doz. Dr. H. Gross
Institut fur Organische Chemie
der Deutschen Akademie der Wissenschaften zu Berlin
Rudower Chaussee 5
X 1199 Berlin-Adlershof (Germany)
Dip1.-Chern. L. Bilk
Forschungsabteilung des VEB Berlin-Chemie
Glienicker Weg 180
X 1199 Berlin-Adlershof (Germany)
[l] W. Rittel, B. Iselin, H . Kappeler, B. Riniker, and R. Schwyzer,
Helv. chim. Acta 40,618 (1957).
[2] G. W. Anderson, J . E. Zimmerman, and F. M . Callahan, J.
Amer. chem. SOC.86, 1839 (1964).
[3] M . Frankel, D . Ladkany, G. Gilon, and Y. Wolman, Tetrahedron Letters 1966, 4765.
Erratum
The Authors of the Communication entitled "The Structure
of Juvenile Hormone", Angew. Chem. internat. Edit. 6, 179
(1967) are H. Roller, K . H. Dahm, C . C . Sweeley, and B. M .
Tvost, and not H . RoIier, K. H . Dohm, C. C. Sweety, and
B. M. Trost, as stated.
C 0 NFE R E N C E R E P 0 RTS
Organometallicand Hydrogen Compounds of Some
Transition Metals
IMPh~(LiPh)41.n(C2H5)20
By B. Sarry [*I
In the absence of air and moisture, anhydrous halides of
transition metals react in various ways with ethereal solutions
of phenyl-lithium.
Nickel and cobalt halides are reduced to catalytically active
metal powders:
MXn
n
+ n LiPh + M + n LiX + 2Ph2
(1)
Organometallic compounds are not formed, nor are hydrides
or hydrido complexes of the metals obtained in the presence
of hydrogen. Hydrogen leads merely to the formation of
lithium hydride:
This reaction is accelerated by cobalt, whereas nickel acts as
catalyst for concurrent hydrogenations.
Tungsten, niobium, and tantalum pentabromides are reduced
by phenyl-lithium only as far as the oxidation state +2. Diphenyl derivatives of the metals are formed, which react
with the excess of phenyl-lithium present to form organometallic complexes.
Angew. Chem. internat. Edit.
/ Vcl. 6 (1967) / No. 6
3
+ 5 LiBr + -2
Ph2
(3)
These products are dark brown to black, finely crystalline
substances, which are extremely susceptible to oxidation and
hydrolysis and are insoluble in petroleum ether, somewhat
soluble in ether, and readily soluble in benzene or dioxane.
The solvate ether (n = 3.5 to 4) is so firmly bound that it is
retained even on recrystallization of the complexes from
benzene.
Ethereal or benzene solutions of these compounds react with
elemental hydrogen - the tungsten compound appreciably
faster than the niobium compound - to form organometallic
hydrido complexes. This reaction gives the black WH(LiPhl2,
which is initially soluble in ether, but which becomes
insoluble on precipitation by hydrocarbons. The niobium
compound has, so far, yielded two similarly insoluble
complexes containing one or two hydride hydrogen atoms,
repectively, per niobium atom.
In accord with the position of iron in the Periodic Table,
iron(m) chloride can react in either way. Above 0 O C reduction
occurs in agreement with equation (I), yielding a mixture of
very finely divided pyrophoric iron and ether-insoluble
lithium chloride. Reaction at about -1 5 "C leads to an ethersoluble product which, after separation from the lithium
chloride formed simultaneously and from the excess of
57 1
phenyl-lithium, can be precipitated by petroleum ether as a
dark reddish-brown, powder which is extremely sensitive
to air and moisture.
When a phenyl-lithium solution (from bromobenzene)
containing lithium bromide is used, the products has
the composition Fe(LiPh)yLiBr, but when a solution (from
diphenylmercury) free from lithium bromide is used the
composition is Fe(LiPh)s. It is formed according to the
equation :
3
FeCI3 + 8 LiPh e Fe(LiPh)s + 3 LiCl+ --Phz
2
(4)
A small amount of an hydridoiron complex is formed
simultaneously which, after isolation, is insoluble in ether.
The hydride hydrogen is provided by oxidation of phenyllithium to biphenylylenedilithium.
Lecture at Kiel on November 24th. 1966
[VB 50 IE]
German version: Angew. Chem. 79, 537 (1967)
[*I Prof.
Dr. Brigitte Sarry
Institut fLlr Anorganische und Analytische Chemie der
Technischen Universitat
Hardenbergstrasse 34
1 Berlin 12 (Germany)
Chemistry and Stability of Lead(1v) Compounds
By F. Huber[*]
The stability and structural relations of Pb(1v) and Pb(n)
compounds cannot be explained by means of completion of
the 6s orbitals11-21 (‘‘inert electron pair”). In the third and
fourth main groups the decrease in stability of the maximal
valency can be correlated satisfactorily with the decrease in
covalent bond strength131 only for the chlorides. A more
generally valid rule can be derived by assuming Pb(Iv)
compounds to provide a n intramolecular redox system and
by attending more strictly to the ionic contribution to the
valence 141.
In contrast to PbF4, PbC14 cannot be obtained by direct
halogenation of Pb(n) halides; chlorine oxidises only complexbound PbCIz, presumably in accord with PbC13e + Cl2 +
[PbC151e and PbC142’ + Clz + [PbC16]Ze. PbC14 is then
obtained from the isolated hexachloroplumbates(Iv), preferably from [(CzH5)3NH]z[PbCl6]. PbBr4, PbI4, Mz[PbBrs],
and Mz[PbI6] ( M = cation) have not been prepared; the
compounds described in the literature as [CqH7NH]z[PbBr6]
and [ C ~ H ~ N H ] Z [ P
I ~ ] in fact halogenoplumbates(rr),
[51~ are
which are formed by addition of halogen (set free in the
“oxidation” of B r e or 10 by Pb(rv)) to the quinolinium cation
CgH7NH+. PbC14 forms complexes PbC14.2Z, which are
more stable than PbC14, provided that Z is not susceptible
to oxidation [Z = pyridine, q u i n o h e , or (C6H5)3PO].
etc., decompose
Complexes with amines, ( C ~ H S ) ~ P
ethers,
,
more orless rapidly, and partially even below 0 “C. Similar relations between stability and susceptibility of the cation to oxidation can be demonstrated for hexachloroplumbates(Iv).
Aminolysis of PbC14 occurs through a n intermediate, for
which the formula [NH4]2[PbCId(NH2)2] has been derived.
PbC14 reacts with PC15 to give [PC14]2[PbC16], and with
SbCl5 to give a complex, presumably [Pbc1~][SbCkj]~.
The ease of preparation and the stability of organolead complexes depend o n the number and nature of the anionic groups
X bound to Pb, and o n the nature of the organic groups R.
Donor-acceptor complexes of PbR4 are unknown, and those
of R3PbX are unstable; nevertheless, complexes of various
compositions can be obtained from RZPbXz, e.g. with
pyridine, ethylenediamine, and 3-azapentamethylenediamine.
The coordination number (CN) 6 is usual in these cases, and
CN 5 is unusual; there are indications of C N 8, e.g. in the
complex [ ( C ~ H ~ ) Z P ~ ( ~ I I ) ~ ] I Z .
5 72
The compound R2PbHal2.4 C5H5N can be regarded as the
ionic complex [ R ~ P ~ ( C ~ H S N ) ~ ] H ~ I ~ .
Stereoisomeric chelates R2Pb(ox)2 (Hox = I-hydroxyquinoline) can be prepared from RzXPbox by reaction
with NH3 or with NH3 and Hox. In RzXPbox the coordination number depends on the nature of the ligands, on the
concentration, and on the temperature; in solution CN is
often 5, and in the solid state presumably 6.
The compounds RPb(ox)3 avoid CN 7 since two of the ox
groups are bidentate and the third one is unidentate. Attempts
to obtain compounds of the type M[RzPbX3] gave halogenoplumbates(rr) M[PbX3], with elimination of the alkyl group R
as ethane (R = CH3) or alkane/alkene mixtures (R = C2H5
etc.).
Lecture at the Humboldt University, Berlin, on November 18th, and
at the Freie Universitat, Berlin, on November Z l s t , 1966
[VB 51 IE]
German version: Angew. Chem. 79, 585 (1967)
[*I Priv.-Doz. Dr. F. Huber
Institut fur Anorganische Chernie und Elektrochemie
der Technischen Hochschule
Ternplergraben 55
51 Aachen (Germany)
[I] H. G. Grimm and A . Sommerfeld, Z . Physik 36, 36 (1926).
[2] N. V . Sidgwick: Some Physical Properties of the Covalent
Link in Chemistry. Oxford University Press, London 1933; Ann.
Reports Progr. Chem. 30, 120 (1933).
[3] R. S. Drugo, J. physic. Chem. 62, 353 (1958).
[4] F. Huber, unpublished.
[5] A . Classen and B. Zuhorski, 2. anorg. allg. Chem. 4 , 100
(1894).
Boron Azides and Boron Imides
By P . Paetzold[*I
Thermal or photolytic decomposition of diorganylboron
azides leads to the formation of rearrangement products in
high yields. The decomposition may be formulated as in eq. (a),
where n = 2 for R = aromatic ligand; or n = 3 for R = aliphatic ligand; (RNBR), = rearrangement product.
RzBN3
---f
Nz
1
+(RBNR),
n
(a)
The tetraaryl-l,3,2,4-diazadiboretidines
( I ) , n = 2, which are
isoelectronic with cyclobutadienes, are extremely sensitive t o
oxidation. Kinetic measurements of the decomposition of
diarylboron azides show that they are the more stable the
better electron-donors the aryl groups are, although Saunders
and Ware observed the opposite relation for decomposition
of triarylmethyl azides 111. On decomposition of azides of the
type ( C ~ H S ) R B N
the
~ aryl group R migrates the more readily
(relative to the C6H5 group) the more strongly it attracts
electrons and the bulkier it is according to the following
series: m-trifluoromethylphenyl > o-tolyl > a-naphthyl >
phenyl >p-chlorophenyl > p-tolyl. The kinetic measurements
and the migratory tendencies accord with a synchronous mechanism for the diorganylboron azide rearrangement.
Bis(dialky1amino)boron azides are more stable thermally
than the diorganylboron azides; when heated to 270 “C they
give indefinite resins. Photolysis leads, in accord with eq. (b),
to the formation of rearrangement products in good yields,
namely, to tetrakis(dialkylamino)-l,3,2,4-diazadiboretidines
(2) that are susceptible to oxidation and on hydrolysis give,
inter a h 1,l-dialkylhydrazines.
Its vibrational spectra indicate that trimeric dichloroboron
azide has a structure with a planar BN six-membered ring (3)
and contains N-diazonium groups. When this compound is
Angew. Chern. internat. Edit. 1 Vol. 6 (1967)
No. 6
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