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Cyclobutadiene-Metal Complexes as Potential Intermediates in Alkyne Metathesis Flash Vacuum Pyrolysis of Substituted 4-Cyclobutadiene-5-cyclopentadienyl-cobalt Complexes.

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The structure of (3) reveals yet another important detail:
two of the C6H5rings are arranged in parallel planes in
such a way that the rc-systems just fail to interpenetrate (Fig.
1). Their mutual separation of 328pm is considerably shorter
than the van der Waals separation of aromatic compounds
(340pm, cf.
Any further compression of the PCP bond
in (3) or mutual twisting of the PC4 tetrahedra must therefore
lead to strong perturbation of the electronic states, and we
suspect that this is the reason for the mechanically induced
photoeffects. The few other known cases of triboluminescence
of organometallic and organic compounds are similarly characterized by relatively large n-systems in a parallel arrangement1’c.91. It should be noted that the triboluminescence of
such “molecular” examples could not yet be interpreted unequivocally-apart from an indication of strong piezoelectric
charging[”. 91.
Moreover, crystallization experiments on ( 1 ) in benzene
gave a new modification, the diffraction data of which are
compatible with a cubic structure[”! This result again shows
that the packing of (1) in the crystal lattice is possible in
a variety of ways and that the molecular geometry of carbodiphosphoranes can readily adapt to a given situation without
incurring large energy losses. The angular flexibility deduced
from slight energy differences between ( A ) and ( B ) has parallels in the isoelectronic cations R3PNPRy, which were also
found to have widely varying bond angles between 134.6
and 180”[”].Concerning the relative energy levels of the two
isosteric series, mention should be made of a recent theoretical
the predictions of the influence of electrondonating substituents contradict our structural findings
[(1)/(3)]. On the basis of the polar formulation ( A ) , both
the complexing properties of carbodiphosphoranesl’ 3a1 and
their manifold organic reactions become immediately understandable“ 3h1,
Received: January 31, 1979 [ Z 210 IE]
German version: Angew. Chem. 91. 437 (1979)
CAS Registry numbers:
( I 1. 753.1-52-0: ( 2 ) . 57437-91-9; ( 3 ) . 60798-30-3
[I]
[2]
131
[4]
[5]
[6]
171
[8]
F . Ramirez, N . 8.Desai, B. Hansen, N . M r K e l u i e , J . Am. Chem. Soc.
83. 3539 (1961).
a) C. N . M a t t h e w . J . S . Drisroll, 3. E. Harris, R. J . Wineman, J.
Am. Chem. Soc. 84, 4349 (1962); J . S. Driscoll, D. W Grisley, J . L!
Pusringer, J . E. Harris, C . N . M a t t h e w , J. Org. Chem. 29, 2427 (1964);
J . I . Zink, W C. Kuska, J. Am. Chem. Soc. 95, 7510 (1973); G . E.
Hurdr, J . C . Baldwin, J . I . Zink, W C . K a s k a , P . H. Lin, L. Dubois,
ihid. Y9. 3552 (1977); b) G. E. Hardy, J . I . Zink, W C . Kuska. J . C.
Euldwin. &id. 100, 8001 (1978); c) J . I . Zink, Ace. Chem. Res. I / , 289
(1978)
A. T I’iiicenf, P . J. Wheatfey, J . Chem. Soc. Dalton Trans. 1972, 617.
H. S h n i d b a u r , 0. Gasser, J. Am. Chem. Soc. 97,6281 (1975); H . Schmidbaur. 0 . Gusser, M . S . Hussuin, Chem. Ber. 110, 3501 (1977).
E . A V Ebsworiii, i? E. Fraser, D.W H. Rankin, 0. Gasser, H . Schmrdbaur,
Chem. Ber. 110, 3508 (1977).
From diethyl ether, not triboluminescent; monoclinic, space group
C2/c.
a=2203(3),
h=1020(1),
r=102Y(l)pm,
/1=1OY.97(9)”,
V = 2 1 7 2 x lob pm’, Z = 4 ; 918 structure factors [F0=3.0n(F0),
2 ” S 2 0 5 4 5 ” ] . Syntex P2,/XTL, MOK? (i=71.069pm, graphite monochromator). R =0.069.
a) M . S. Flussuin, H . Schmidbuur, Z. Naturforsch. B 3 I , 721 (1976);
b) H . P. F r i t z H . Gehauer, P. Friedrich, P. Ecker, R. Aries, U. Schubert,
ihid. R 3 3 , 498 ((978).
H . LUWbr<JsO,J . Curs, H.-J. Besimann, J. Organomet. Chem. 161, 347
(19781.
Atlqcu..
Y Dusausoy. J . Protus, P. Runaut, 6. Gautheron, G . Tuiriiurier. J . Organomet. Chem. 157. 167 (1978).
Not triboluminescent: a = h = c = 1576(2)pm, Laue classe m3.
R. D. Wilson, R . Bau, J. Am. Chem. Soc. 96, 7601 (1974). and references
cited therein.
C . Glidewell, J. Organomet. Chem. 159. 23 (1978).
a) W C. Kaska, D. K . Miichell, R . F. Reichrlderfer. W D . Korte. J.
Am. Chem. Soc. 96, 2847 (1974). and references cited therein: b) H .
J . Eiwmann. Angew. Chem. X9, 361 (1977): Angew. Chem. Int. Ed.
Engl. 16, 349 (1977).
Cyclobutadiene-MetalComplexes as Potential Intennediates in Alkyne Metathesis: Flash Vacuum Pyrolysis
of Substituted q4-Cyclobutadiene-q5-cyclopentadienylcobalt Complexes[**]
By John R. Fritch and K . Peter C. Vo/ollhurdt[*l
The mechanism of alkyne metathesis [eq. (a)] is a matter
of unresolved controversy. The actual process has only been
observed at relatively high temperatures in the gas phase“ I
and in solution”] over mostly heterogeneous tungsten and
molybdenum catalysts. However, the literature abounds with
examples in which the final product of the interaction of
an alkyne with a transition metal appears to be derived from
initially metathesized or “dichotomized” starting material[3’.
The logical intermediate (1 ) in this reaction”’, has been discounted due to the “unusual stability” of cyclobutadienemetal
complexes, in addition to the fact that their condensed phase
thermal decomposition fails ro g i w ulkyne products[4!
We would like to report that: (1) cyclobutadiene-cyclopentadienylcobalt complexes cleanly decompose on heating in the
gas phase to regenerate their component acetylenes; (2) these
decompositions require intermediate bis(a1kyne)cobalt complexes; (3) rotation and reclosure of the complexed alkynes
to cyclobutadiene rings competes with decomplexation; and
(4) migration of cobalt along the two triple bonds of diyne
ligands does not occur.
Flash pyrolyses at short contact times (ca. 0.005s, ui.
lo-’ torr) were carried out as described earlier‘’]. Product
yields were independent of the amount of material pyrolyzed
and of whether or not the pyrolysis tube was cleaned before
reuse, thus ruling out wall effects, in particular secondary
cobalt-catalyzed wall reactions. q4-Tetraphenylcyclobutadiene-q 5-cyclopentadienylcobalt (2 )I6] was pyrolyzed at
726°C to give (at 47% conversion) 89% of isolated diphenylacetylene.Thepyrolyses ofthe substituted diethynyl derivatives
(3)-(6) summarized in Table 1 are instructive, particularly
under conditions of incomplete conversion.
[*] Prof. Dr. K. P. C . Vollhardt. J. R. Fritch
Department of Chemistry, University of California, and the Materials
and Molecular Research Division, Lawrence Berkeley Laboratory
Berkeley, California 94720 (USA)
[**I We are grateful for support by the Division of Chemical Sciences,
Office of Basic Energy Sciences, U.S. Department of Energy (Contract
No. W-7405-Eng-48), NSF, NIH, Chevron Research Company, Pressure Chemical Corporation, and Silar Laboratories, Inc. K . P . c‘. L! is a Fellow
of the A. P. Sloan Foundation, 1976--1980, and a Camille and Henry Dreyfus
Teacher-Scholar, 1978-1983: J . R. F. is the recipient of a Regents’ Predoctoral Fellowship (1977) and a Gulf Oil Fellowship (1978).
Chrrn. 1111.Ed. Engl. 18 ( 1 9 7 9 ) No. 5
0 Verfag Chetnir, GmbH, 6940 Weinheini, 1979
409
0570-0833179 :0505-0409 3 02.50/0
Table I , Alkynes from decomposition of cyclobutadiene complexes (3)-(6).
Starting
material
T r C ] [c]
Yield
( 3 ) [el ( 4 )
[%I [a, d. r]
(3) [he]
775
702
675
[hl
0.04
0.04
( 4 ) [b. i]
780
682
652
640
0.29
17.8
34.7
49.2
151
676
(6)
70 I
[h]
0.02
10.03
(6) [g] ( 8 i
(5)
1.9
17.3
32.1
0.41
1.5
2.0
32.0
20.5
16.3
1.2
I .7
[h]
0.07
0.06
0.05
74.8
59
43.7
31.9
34.8
2.90
17.4
30.71
30.9
__
0.06
1.1
[h]
7.17
(12)
18.3
12.0
9.8
1.1
0.58
0.16
0.20
11.9
5.70
__
[a] A cobalt mirror formed on the surface of the pyrolysis tube. Traces
of acetylene were (incompletely) trapped in all reactions. In addition to
the alkyne products indicated, compounds derived from the cyclopentadienyl
moiety were isolated and identified: cyclopentadiene, dihydrofulvalenes, and
naphthalene [7]. No cyclobntadiene dimers were detected. [b] These starting
materials polymerize on standing and were freshly chromatographed before
each run. [c] At the center of the tube. [d] Determined by G C and NMR
integration. Polymer forms a t both entrance and exit to the oven, accounting
for incomplete mass balances. [el (3) leads to ( 5 ) aia the diethynylcyclobutadiene rearrangement [Saj. [f] The absence of butadiyne, hexatriyne, trimethylsilylethyne, trimethylsilylhexatriyne, bis(trimethylsilyl)ethyne, and bis(trimethy1silyl)butadiyne was ascertained by FID-GC and GC/mass spectroscopy.
[g] Identified by G C mass spectroscopy and independent synthesis [lithiation
followed by trimethylsilylation of 1,3-diethynylcyclobutadiene-cyclopentadienylcobalt [5a]: (6): yellow crystals; m.p. 156--158°C; m/e 368 ( M ’ ,
lOO%), 124 (CpCo, 54%); T (CCI4)4.97 (s, 5H), 5.45 (s, 2H), 9.81 (s, 18H);
IR: 2135cm- ( C S C ) . [h] Undetectable by GC/mass spectrometry and
FID-GC. [i] ( 4 ) was erroneously reported [5a] t o be stable t o 700°C
under the pyrolysis conditions; correct is 600°C.
’
Several features are noteworthy. Firstly, efficient conversion
of the cyclobutadiene ring to the corresponding alkynes is
observed. Second, as demonstrated by the control pyrolysis
of ( 5 ) , (3) is decomposed largely via the intermediacy of
R
I
cocp
I
R--E --_=
Scheme 1 . Pyrolysis of (31-(61.
(lo)
R=Si(CH&; *=detected compound.
( 5 ) reached by the low-energy and mechanistically totally
distinct “diethynylcyclobutadiene rearrangement”15a1.Third,
the free energies of activation[’] for the decomposition of
(2) and (4)-(6) (AG” ~47-SO kcal/mol) are appreciably
higher than that for the (3) ---t ( 5 ) rearrangement
(AG * = 37 kcal/mol) but considerably lower than the CpCobond strength (64k~al/mol)[’~.Fourth, unprecedented mutual
interconversion (but not complete equilibration) of the cyclobutadiene starting complexes is observed.
410
The reproducibility of the data, absence of wall effects,
known stability of free cyclobutadiene to flash pyrolysis conditionsLLol
even above SOOT, and the low pressures employed
ruling out bimolecular reaction pathways” ‘I suggest the
mechanism in Scheme 1 to rationalize the results.
Isomer ( 3 ) pyrolyzes via ( 5 ) and the postulated complexes
( 9 ) and (I]) to give the observed major products (8) and
(12), respectively. The new cyclobutadiene isomer (6 j is derived from (9) by rotation and reclosure. The absence of
bis(trimethylsi1yl)ethyne indicates a relatively high activation
energy to decomposition of (3) via this pathway. The detection
of small quantities of ( 4 ) demonstrates the accessibility of
intermediate (7) from (3). Isomer ( 4 ) enters the reaction
manifold through ( 7 ) , giving mainly trimethylsilylbutadiyne
(8). It can also reclose to ( 3 ) , the latter rapidly giving ( 5 )
and its decomposition products uiu the diethynylcyclobutadiene
The presence of traces of ( 6 ) shows
the possibility of completing two opening-rotation-reclosure
sequences in the time scale of the experiment. Decomposition
of ( 6 ) gives products consistent with this picture, again implicating intermediates (9) and (I I ).
The fact that the yield of (8) is always much greater than
the yield of (6) [from (3) or ( 5 ) ] and of ( 5 ) [from ( 4 )
or ( 6 ) ] indicates that decomplexation from the bisalkyne
complexes is more facile than recyclization. The absence of
other cyclobutadiene isomers and their ultimate alkyne products in the pyrolyzates of (3)-(6) (see Table I , footnote
[f]) makes diacetylene shifts (e. g. (7) 2 (9), (9) 2 ( I O), etc..)
unlikely.
Scheme 1 suggests that cyclobutadiene-metal complexes are
potential intermediates in alkyne methatheses.
Received: January 29, 1979 [ Z 202a IE]
German version: Angew. Chem. 91.439 (1979)
CAS Registry numbers:
(31,67378-02-3; ( 4 ) , 67378-01-2; 1 5 ) , 67378-03-4; (6), 69991-02-2; ( 8 ) . 452606-1 ; (121, 21 752-86-3
[I] F. Pennella, R. L. Banks, G . C. Bailey, Chem. Commun. 1968, 1548;
A . Mortreux, M . Elanchard, Bull. SOC. Chim. Fr. 1972, 1641; J . A .
Moulijn, H . J . Reitsma, C. Boelhouwer, J . Catal. 25, 434 (1972); H .
Hucker, R. Musch, Makromol. Chem. 176, 3117 (1975).
[2] A. Mortrcux, M . Blatrchard, J. Chem. Soc. Chem. Common. 1974, 786;
A. Morrreux, M . Blanchard, Metathesis Symposium, Mainz, Germany,
January 1976; A . Morrreux, F. Petit, M . Blanchard, Tetrahedron Lett.
1978, 4967, and references cited therein.
[3] See, for example, U . Kriierke, W Hiibel, Chem. Ber. 94, 2829 (1961);
W Hiibel, R. MerPny, J. Organomet. Chem. 2, 213 (1964); A. J. Hubert,
J. Chem. SOC.C1967, 1984; G. M . Whitesides, U! J . Ehmann, J. Am.
Chem. Soc. 91, 3800 (1969); H . D i d , H. Reinheimer, J . Moffat, P.
M . Maitlis, ibid. 92, 2276 (1970); R . E . King, I . Hnidur, C . U! Euvenson,
ibid. YS, 2508 (1973), and references cited therein; H . B. Chin. R . Buu,
ihid. 95, 5068 (1973); H . Hoberg, R. Krause-Going, C . Kriiger, J . C.
Sekutowski, Angew. Chem. 89. 179 (1977); Angew. Chem. Int. Ed.
Engl. 16, 183 (1977), and references cited therein; R. B. King, Ann.
N. Y. Acad. Sci. 295, 135 (1977); E . Sappa, A . Tiripicchio, A . M . M .
Lanfredi, J. Chem. Soc. Dalton Trans. 1978,552.
[4] P. M . Maitlis, Adv. Organomet. Chem. 4 , 95 (1966); R. C . Dickson,
P . J . Fraser, ibid. 12, 323 (1974); A . Efraty, Chem. Rev. 77, 691 (1977).
In the only gas phase study, cyclobutadienetricarbonylironpyrolyzed
to a complex mixture: E. Heduju, I . S. Krull, R. D. Miller, M . E.
Kent, P. F. D’Angelo, P. Schissel, J. Am. Chem. Soc. 91, 6880 (1969).
[5] a) J. R. Fritch, K . P. C. Vollhardt, J. Am. Chem. SOC.100, 3643 (1978);
b) K. P. C. Vollhurdt, L. S. Yee, ibid. 99, 2010 (1977); A . J. Barkouich,
E. S. Strauss, K . P . C . Vollhardt, h i d . 99, 8321 (1977).
[6] M . D.Rausch, R. A . Gcnetti, J. Org. Chem. 35, 3888 (1970).
[7] E. Hedaya, Acc. Chem. Res. 2, 367 (1969).
[S] Approximate free energies of activation (error margin k 2 kcal/mol)
were calculated by using four known gas phase pyrolysis reactions
(thermolyses of cyclopentadiene dimer, norbornene, cycloheptatriene,
and 1,4-cyclohexadiene) as standards to estimate contact times as a
function of temperature and molecular weight.
191 J . A . Connor, Top. Curr. Chem. 71, 71 (1977)
A n g e ~ , Chem.
.
l n t . Ed. E i i q l . 18 (19791 No. 5
0 Verlug Chemie, GmhH, 6940 Weinheim, 1979
0570-0833/79:05~~5-0410$ 02.50/0
D. W M c N e i l , P . F. D'Angelo, P. Schissel,
J . Am. Chem. SOC.91, 1875 (1969).
G. Sryhold, Angew. Chem. 89,377 (1977); Angew. Chem. Int. Ed. Engl.
16, 365 (1977).
[lo] E. Hedaya, R. D. Miller,
[I
11
R. P. Thummel, D. K. Kohli, J. Org. Chem. 43, 4882 (19710.
B. M . Mikkailoo, T K . Kozminskaya, Zh. Ohshch. Khim. 26, 2042 (1956):
Chem. Ahstr. 51, 5072 (1957).
R. Gray, L. G . Harrufi J . Krymowski, J . Peterson, Y Boekelherde, J.
Am. Chem. Soc. 100, 2892 (1978); P. Schiess, M . Heitzmann, Helv. Chim.
Acta 61, 844 (1978).
MS: m/e=131.0732 (calc. 131.0735, M t , 84%), 130 (loo%), 91 ( 2 5 " / ) ,
65 (42 %), 51 (21 %), 39 (25 %); 'H-NMR (CDCI,): 6=6.96 (br. s, I H),
3.30 (m, 4H), 2.98 (m. 4 H ) ; "C-NMR (CDCI,): 0=26.8 (t, J c . -H
=139,9Hz), 34.2 (t, 138.6Hr). 124.4 (d, 163.5Hz), 138.6. 161.7: U V
(95% ethanol): ;.m,,=286nm sh (Igc=3.94), 289 (3.97), 292sh (3.95).
299sh 13.74); IR (CHCI,): vm,,=2980, 2937, 1599, 1369, 1244, 9 0 5 c m - '
R. P. Thummel, D. K . Kohli, J. Org. Chem. 42, 2743 (1977).
For an independent synthesis of (2). see R. P. Thummel. D K . Knhli.
Tetrahedron Lett. 1979, 143.
1,2,4,5-Tetrahydrodicyclobuta[b,e]pyridine[**1
By Alaric Naiinan and K . Peter C. Vollkardt~]
Benzenoid hydrocarbons fused to strained rings have been
the target of recent synthetic efforts aimed at the preparation
of aromatic rings in which bond fixation or other perturbations
of aromaticity might be observed. So far evidence for the
former has been tenuous[']. The decreased aromaticity of pyridine [estimated at 21 k~al/mol][~]
when compared with benzene suggests that it might more easily be subjected to bond
localization. Some support for this is found in the physical
and chemical properties of cyclobuta[b]- and cyclobuta[c]pyridinec3].We report the synthesis of (2), presently the most
strained annelated pyridine.
Flash vacuum pyrolysis (SOOOC,
torr) of dichloride
( 1 )[41 proceeds through double HC1-eliminationrsl,providing
on basic workup the pyridine (2) in ca. 50% yield. Fractional
sublimation (40"C,
torr) to separate (2) from ( I )
furnished colorless crystals (m.p. 117.5-118.5"C). The structural assignment follows from spectral data and chemical
propertieP1.
Reaction of (2) with neat bis(trimethylsi1yl)acetylene
(200°C, 12h) followed by oxidation with dichlorodicyano-pbenzoquinone (in benzene, 8 0 T , 2 h) and desilylation (conc.
H 2 S 0 4 ,80°C, 1 min.) gave acridine.
The isolation of (2) under conditions conducive to equilibration with the ring-opened o-quinodimethane ("o-lutidylene") (3) suggests appreciable residual aromaticity in (2).
This is also indicated by the nuclear magnetic resonance data
and the electronic spectrum. As might be expected, the latter
shows bathochromic shifts and larger extinction coefficients
in comparison with suitable bisannelated
The significant ring strain experienced by ( 2 ) is likewise reflected in
the I3C-NMR chemical shifts and 13C-H coupling constan ts['I.
Received: February 2, 1979 [Z 202b IE]
German version: Angew. Chem. 91,440 (1979)
CAS Registry numbers:
( I ) , 69961-31-5; ( 2 ) , 69961-32-6; ( 3 ) , 69961-33-7
Cyanohalophosphates(rr1)-Hypervalent
taining hS-Phosphor~(~~r)[**]
By Alfred Sckmidpeter and Franz Zwasckka[*]
One of the typical reactions of halide ions is their combination with a halogen molecule X2 to give the linear trihalide
ions X i . If different halogen atoms are involved, then the
more electropositive one assumes the central position[']. In
accord with its postulated pseudohalogen character"], the
dicyanophosphide ion ( I ) adds bromine and iodine at room
temperature to give anions (3) of X i type with P(CN)2 as
central member. These hypervalent anions are dicyanodihalophosphates(rI1).Their crown ether-sodium salts can be isolated
in crystalline form.
Oxidative addition of halogen to ( I ) can be resolved, at
least formally, into two steps:
It is surprising that the reaction does not lead merely to
dicyanohalophosphanes (2) but beyond that to the hypervalent
species (3)I3). The ion ( 3 ) , X=Br or I, does not dissociate
in solution, as is apparent from the characteristic upfield
shift of the 31P-NMR signal (see Table 1). Under the same
conditions, addition of chlorine to ( 1 ) gives only ( 2 ) , X = C1.
Addition of cyanogen bromide or iodide instead of halogens
gives the tricyanohalophosphates(1u)( 4 ) , X = Br or I.
These results suggest that phosphorus tricyanide ( 5 ) s (2),
X = CN, might add halide ions to form the hypervalent anions
(4):
P(CN)3 + X-SP(CN)3X-
[*] Prof. Dr. K. P. C. Vollhardt, A. Naiman
Department of Chemistry, University of California, and the Materials
and Molecular Research Division, Lawrence Berkeley Laboratory,
Berkeley. California 94720 (USA)
[*'I
We are grateful for support by the Division of Chemical Sciences,
Office of Basic Energy Sciences, U. S. Department of Energy (contract No.
W-7405-Eng-48)and NIH (CA 2071 3). K . P . C. K is an A. P. Sloan Foundation
Fellow ( I 976-1 980) and a Camille and Henry Dreyfus Teacher Scholar
(1978-1983); A. N . is the recipient of a Regents' Fellowship (1977--1979).
For recent work: C. Santiago, R. W Gandour, K . N . Houk, W Nutakul,
W E . Crave?, R . P. Thummel, J. Am. Chem. Soc. 100, 3730 (1978);
R. P Thummel, W Nutakul, J. Org. Chem. 42, 300 (1977); 43, 3170
(1978); D. Dacalian, P . J . Garratt, M . M . Mansuri, J. Am. Chem. Soc.
1110, 980 (1978); P. Perkins, K . P. C. Vollhardt, Angew. Chem. PO, 648
(1978); Angew. Chem. Int. Ed. Engl. 17, 615 (1978).
121 M . J . S . Dewar, A. J . Harget, N . Trinajstic, J. Am. Chem. Soc. 91,
6321 (1969); G . Hiifelinger, L. Steinmann, Angew. Chem. 89, 48 (1977);
Angew. Chem. Int. Ed. Engl. 16, 47 (1977).
[l]
(5)
(4)
Compound ( 5 ) does indeed react with crown ether-sodium
chloride, bromide, and iodide to form mobile equilibria with
( 4 ) (NMR spectroscopy). The chemical shift h31P decreases
linearly with addition of halide until the equivalence point
is reached, and then stays essentiallyconstant. All the equilibria
(including that with X=C1) lie far to 'the right, and all three
crown ether-sodium salts can also be isolated as crystals.
[*I Prof. Dr. A. Schmidpeter, Dip].-Chem. F. Zwaschka
Institut fur Anorganische Chemie der Universitat
Meiserstrasse 1, D-8000 Miinchen 2 (Germany)
['*I Cyanopbosphorus Compounds, Part 2. This work was supported by
the Deutsche Forschungsgemeinschaft and the Fonds der Chemischen Industrie.-Part 1 : [l].
A n g i w . Ciirm. I n t . E d . Engl. 18 (1979) No. 5
0 Verfag Chemie, GmbH, 6940 Weinheim, 1979
Anions Con-
411
0570-0833/791050~-0411 $ O2.50/0
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intermediate, alkyne, pyrolysis, complexes, cobalt, cyclopentadienyl, cyclobutadiene, potential, metathesis, vacuum, metali, flash, substituted
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