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Coupling of Alkynes with Carbene Ligands to Tungsten-coordinated Cyclopropenes and Their Stereoselective Isomerization to Vinylcarbene Complexes.

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from 1.69 to 4.51). Full-matrix least-squares refinement of positional and
anisotropic thermal parameters of all non-H atoms and an overall isotropic thermal parameter for H atoms converged at a final R value:
0.043 w R = 0.051; w - ' = d ( F ) for 5267 unique reflections with
I > 2.5a(I) [9].
[71 H. 0. Kalinowski, S. Berger, S. Braun in: Carbon-13 N M R Specfroscopy,
Wiley, Chichester 1988, p. 549.
[81 Crystal structure data for 3: C,,H,,C13N,TaZn, M = 613.11, orthorhombic space group P2,2,2,, a = 9.725(2), b = 10.436(2), c = 20.766(3) A,
V = 2107.5(7) A3, Z = 4, pralcd= 1.932 gcm-j, p(MoK,) = 66.8 cm-l. A
red-brown block-shaped crystal (ca. 0.37 x 0.63 x 0.80 mm) of3, mounted
on a glass fiber, was used for data collection on an Enraf-Nonius CAD-4diffractometer at 100 K with Zr-filtered Mo,. radiation (em,, = 29.4") The
structure was solved with Patterson and Fourier techniques (SHELXS86). H-atoms were introduced at calculated positions (C-H = 0.98 A). An
empirical absorption correction was applied (DIFABS). Full-matrix leastsquares refinement converged at a final R value: 0.034 wR = 0.054;
= 0 2 ( F ) 0.0017(F)2 for 4746 unique reflections with I > 2.5u(I) 191.
[9] Further details of the crystal structure investigation are available on request from the Director of the Cambridge Crystallographic Data Centre,
University Chemical Laboratory, Lensfield Road, GB-Cambridge CB2
I E W (UK), on quoting the full journal citation.
[lo] For recent examples of bridging aryl functions see: G. van Koten, J.
Organomel. Chem. 400 (1990) 283; P. R. Markies, G. Schat, 0. S. Akkerman, F. Bickelhaupt, W J. J. Smeets, P. van der Sluis, A. L. Spek, ibid. 393
(1990) 315.
[I 11 A. W. Gal, H. van der Heijden, J. Chem. Soc. Chem. Commun. 1983,420.
Coupling of Alkynes with Carbene Ligands to
Tungsten-coordinated Cyclopropenes and
Their Stereoselective Isomerization to
Vinylcarbene Complexes **
By Helmut Fixher,* Josef Hofmann, and EIvira Mauz
Dedicaied to Professor Paul Binger on the occasion
of his 60th birthday
Reactions of cyclopropenes with transition metals find
many uses in organic synthesis.['' For some of the transition
metal-catalyzed reactions the sequence cyclopropene +
cyclopropene complex +vinylcarbene complex (or metallacyclobutene) +organic product has been postulated.[2]Both
cyclopropene complexesr3.41 as well as vinylcarbene comp l e x e ~ [ ~ *and metallacyclobutenes16)have been prepared
from transition metal complexes and cyclopropenes. So far
however, it has not been possible to verify the step cyclopropene complex + vinylcarbene complex.
Cyclopropene complexes are generally prepared by ligand
substitution. Their synthesis from carbene complexes and
alkynes has thus far never been reported, though the intermediary formation of a cyclopropene in the reaction of 2-butyne with a cationic benzylidenedicarbonyI(cyc1opentadieny1)iron complex has been postulated on the basis of the
reaction product^.^'] We now report the synthesis of isolable
cyclopropene complexes by addition of alkynes to carbene
complexes and the demonstration of stereoselective intramolecular ring opening to give vinylcarbene complexes.
reacts at - 80 "C in one to
The benzylidene complex 1 arB1
two hours with an equimolar amount of phenylacetylene to
give the cyclopropene complex 2a. This is stable only below
ca. - 40 "C. Above - 30 "C, 2a rapidly isomerizes in solution
to the vinylcarbene complex 3a. Upon reaction of 1 a with
- 70%
R = H
b , R = Me
phenylacetylene on a preparative scale, mixtures of 2a (major product) and 3a are generally obtained which are difficult to separate. In contrast to 2 a however, 3 a already reacts
rapidly at -70 "C with diethylpropynylamine to give 4. The
compounds 2 a and 4 can be separated chromatographically
at -7O"C, hence 2a is obtainable in pure form in this way.
The structure of the cyclopropene complex 2a could be
confirmed spectroscopically. The IR spectrum indicated a
pentacarbonyl complex. The benzylidene-H NMR signal is
shifted upfield by more than 14 ppm compared to that in 1 a,
while the signal of the original sp-CH atom of phenylacetylene is shifted ca. 2 ppm downfield. The assignments
are supported by the spectrum of [D]2a (obtained from 1 a
and Ph-CEC-D). The I3C-NMR spectrum of 2a shows, in
addition to the signals for the CO substituents and the two
phenyl groups, signals for three further carbon atoms between 6 = 34 and 65, of which two couple with the tungsten
atom (J(W,C) = 16 and 19 Hz). Signals at low field
(6 > 210), characteristic for carbene complexes, are absent.
According to the NMR spectra the rearrangement of 2a to
3a is stereoselective; carbene complexes isomeric with 3a
could not be detected. The structure of 3a follows unequivocally from the characteristic downfield position of the carbene-H and carbene-CNMR signals (6 = 16.64 and 331.1,
resp.). Above ca. - l O T , 3a reacts further to give 5 (major
product) and two other, so far not fully characterized complexes. The formation of carbene-bridged dinuclear complexes such as 5 is typical for the thermolysis of strongly
electrophilic carbene complexes in inert solvents.L8b, ''1 Xray structure analyses were carried out on the complexes 4,
5 (Fig. l)I9] and 6 (see below). In all compounds the two
phenyl groups are cis oriented.
When a solution of 2a in the presence of triphenylphosphane is warmed from - 70 "C to - 10"C, the ylide complex
6 is formed. It follows, therefore, that the rearrangement
2 a .+. 3 a most likely proceeds intramolecularly. In the case
of a dissociative process (cleavage of the cyclopropene and
attack of the resulting pentacarbonyltungsten fragment at a
C-C o-bond of the cyclopropene with ring opening to give
Prof. Dr. H. Fischer, Dr. J. Hofmann, DipLChem. E. Mauz
Fakultat fur Chemie der Universitat
Postfach 55 60, W-7750 Konstanz 1 (FRG)
This work was supported by the Stiftung Volkswagenwerk, the Fonds der
Chemischen Industrie, and the Land Baden-Wurttemberg (Project: MetalCentered Substrate Transformations).
0 VCH Verlagsgesellschaft mbH.
W-6940 Weinheim. 1991
0570-0833/91/0808-0998$3.50+ .2S/O
Angew. Chem. Inr. Ed. Engl. 30 (1991) No. 8
5 : Yield 25%; m.p. 129°C; 'HNMR (CDCI,, 30°C): 6 = 4.27 (s, p-CH),
6.9-7.4(rn,Ph),9.85(~, =CH); "CNMR(CDCI,,O"C):b = 93.2(=C), 126.0
(=C), 128.3, 128.7, 128.9, 129.1, 130.0, 130.5, 134.8, 140.8 (Ph), 161.3 (p-C),
195.1 (J(W,C) = 122 Hz, CO), 200.0 (CO), 206.6 (br, CO); IR (hexane): i(C0)
[cm-'1 = 2087 s, 2049 vs, 2008 s, 2000 s, 1982 vs, 1952 s, 1930 m.
6: Yield 65%; decornp. above 80°C; 'HNMR (CD,Cl,, - 70°C): b = 3.28 (d,
*J(P,H) = 12.5 Hz, WCH), 6.51 (d, J(P,H) = 4.0Hz), 6.6-8.0 (m,Ph); IR
(hexane): i(C0) [cm-'1 = 2059m. 1962 w, 1915 vs, 1900s.
Received: February 19 (1991) [Z 4553 IE]
German version: Angew. Chem. 103 (1991) 1013
Fig. 1. Structure of5 in thecrystal (H atomsomitted). Important distances [A],
angles and torsion angles ["I, standard deviations in brackets): W1 -W2
3.119(1), W1-CIO 2.238(8), W2-C10 2.216(8), W2-Cll 2.417(9), W2-Cl2
2.459(8), CIO-Cl1 1.458(10), Cll-C12 1.421(10); Wl-CIO-W2 88.9(3),
W1-W2-CIO 45.9(2), W2-CIO-Cll 79.3(5), CIO-C11-Cl2 116.4(7); W1W2-C10-Cl1 135.6(5), W2-ClO-Cll-CI2 - 55.6(7), CIO-CIl-Cl2C121 164.3(8).
3a) the formation of pentacarbonyl(tripheny1phosphane)tungsten would be expected. This, however, could not be
detected. 6 is apparently formed by nucleophilic addition of
PPh, to 3a. (Phosphanes are frequently used to trap unstable
carbene cornplexe~.~'
Also the p-Me-substituted complex 1 b reacts analogously
to 1 a with phenylacetylene. 2 b is slightly more stable than 2 a
and rearranges somewhat more slowly to 3b. Considerably
more rapid, however, is the ring opening in the cyclopropene
complex formed by addition of p-methylphenylacetylene to
1 a; this complex has been detected NMR spectroscopically
Formally, 3 is formed by insertion of the C=C bond of the
alkyne into the W=C bond of 1. Insertion of electron-rich
alkynes into metal-carbene carbon bonds have long been
known" ',1 2 ] and have been studied in detail.[131However,
the regioselectivity of these insertions and that of those described here are inverse. This shows that insertions of triple
bonds into metal-carbene carbon bonds in coordinatively
saturated complexes can proceed via several associative
The reactions can be carried out both in CH,CI, as well as in CH,Cl,/pentane.
The structures of all the complexes, with the exception of 3a, were confirmed
spectroscopically (IR, 'H, ',C-NMR) and by elemental analyses. 3a was characterized only spectroscopically. X-ray structural analyses were carried out on
complexes 44.
2a: 'HNMR (CD,CI,, -70°C): 6 = 2.81 (s, sp3-CH), 5.20(s, =CH), 6.9-7.5
(m,Ph); "CNMR(CD,CI,, -7O"C):d = 34.0(sp3-C),46.4(J(W.C) = 19 Hz,
=CH), 64.7 (J(W,C)= 16 Hz, =CPh), 125.5, 126.1, 127.7, 128.4, 131.9, 142.6
(Ph), 195.3 (J(W,C) = 127 Hz, cis-CO), 205.1 (J(W,C) = 135 Hz, trans-CO); IR
(hexane): C(C0) [cm-']= 2089m, 1995 s, 1967 s, 1956vs.
3a: 'H NMR (CD,CI,, - 40°C): 6 =7.78 (s, C,H), 6.9-7.7 (m, Ph), 16.64 (s,
W=CH); I3CNMR (CDZCI,, - 40°C): b = 149.2 (CJ, 165.7 (C,), 196.7 (cisCO), 216.1 (trans-CO), 331.1 (W=C); IR (hexane): C(C0) [cm-'] = 2072 s,
1964 vs.
4: Yield 60%; m.p. 102°C; 'HNMR (CDCI,): 6 = 1.33, 1.40 (each t,
J 1 7 . 2 Hz, CH,CH,), 1.52 (s, =CCH,), 3.63 (dq, J = 7.0, 3.1 Hz, 2H, CH,),
4.02 (dq, J = 13.2, 6.7 Hz, l H , NCH,), 4.17 (dq, J = 13.2, 7.3 Hz, 1H NCH,),
5.57 (s, =CH), 6.56 (s, benzylidene-H), 6.9-7.5 (m, Ph); I3CNMR (CDCI,,
room temperature): 6 = 14.0, 14.9, 16.2 (CH,), 47.0, 55.6 (CH,), 127.4, 127.8,
128.8, 129.2, 129.3, 131.5, 136.8, 140.4 (Ph), 121.9, 126.7, 138.6, 148.2 (=C),
198.6 (J(W,C) = 128 Hz, cis-CO), 202.9 (J(W,C) = 126 Hz, trans-CO), 257.0
(J(W,C) = 90 Hz, W=C): IR (hexane): G(C0) [cm-'1 = 2063 m, 1969 w,
1934 vs, 1917 s.
Angew. Chem. I n t . Ed. Engl. 30 (1991) No. 8
a) P. Binger, H. M. Buch, Top. Curr. Chem. 135 (1987) 77; b) M. S . Baird,
ibid. 144 (1988) 137; c) B. Halton, M. G.Banwell in Z. Rappoport (Ed.):
The Chemistry of the Cyclopropyl Group, Wiley, Chichester 1987, p. 12231339.
Cf., for example, P. Binger, B. Biedenbach, Chem. Ber. 120 (1987) 601.
a) J. P. Visser, A. J. Schipperijn, J. Lukas, D. Bright, J. J. deBoer. Chem.
Commun. 1971, 1266; b) S. Fredericks, J. L. Thomas, J. Am. Chem. SOC.
100 (1978) 350; c) H. Lehmkuhl, R. Paul, C. Kruger, Y.-H. Tsay, R. Benn,
R. Mynott, Liebigs Ann. Chem. 1981, 1147.
P. Binger, P. Muller, R. Benn, R. Mynott, Angew. Chem. 101 (1989) 647;
Angew. Chem. Int. Ed. Engl. 28 (1989) 610.
a) J. Klimes, E. Weiss, Angew. Chem. 94 (1982) 207; Angew. Chem. Int. Ed.
Engl. 21 (1982) 205; b) T. Valeri, F. Meier, E. Weiss, Chem. Ber. 121 (1988)
a) R. C. Hemond, R. P. Hughes, D. J. Robinson, A. L. Rheingold,
Organometallics7 (1988) 2239; b) R. P. Hughes, M. E. King, D. J.
Robinson, J. M. Spotts, J. Am. Chem. Soc. 111 (1989) 8919.
M. Brookhart, M. B. Humphrey, H. J. Kratzer, G. 0. Nelson, J. Am.
Chem. SOC.102 (1980) 7802.
a) C. P. Casey, S. W. Polichnowski, A. J. Shusterman, C. R. Jones, J. Am.
101 (1979) 7282; b) H. Fischer, S. Zeuner, K. Ackermann, J.
Chem. SOC.
Chem. SOC.Chem. Commun. 1984,684.
5: monoclinic, P2,/c, a = 15.288(3), b = 10.004(3), c = 16.559(4) A,
= 107.94(2)", V = 2409(1) A,, 2 = 4, p(MoKa),
= 2.24 gem-,,
Nicolet R3m Four-circle diffractometer. Data collection: T = 300 K,
Wykoff scan, o = 1.5-29.3"min-', 4517 independent reflections with
4.0 < 2 8 < 51.0", 3586 with IFa[ > 60(F0). Solution ofstructure by direct
methods (SHELXTL PLUS). R = 0.036, R, = 0.049. Residual electron
density 1.8 e k ' . Further details of the crystal structure investigation are
available on request from the Fachinformationszentrum Karlsruhe,
Gesellschaft fur wissenschaftlich-technischeInformation mbH, W-7514
Eggenstein-Leopoldshafen 2 (FRG) on quoting the depository number
CSD-55336, the names of the authors. and the journal citation.
H. Fischer, S. Zeuner, K. Ackermann, J. Schmid, Chem. Ber. 119 (1986)
Cf. K. H. Dotz, H. Fischer, P. Hofmann, F. R. Kreissl, U. Schubert, K.
Weiss (Eds.): Transition Metal Carbene Complexes, Verlag Chemie, Weinheim 1983.
K. H. Dotz, C. G. Kreiter, J. Orgunomet. Chem. 99 (1975) 309.
H. Fischer, K. H. Dotz, Chem. Ber. 113 (1980) 193.
Ammoniumyl Salt-Induced Diels-Alder Reaction
of Ketenes-Control of [2 + 21 vs. [4 + 21
Selectivity **
By Michael SchmitteP and Heinke von Seggern
Dedicated to Professor Horst Prinzbach
on the occasion of his 60th birthday
[2 21-Cycloaddition products are formed exclusively
with a remarkable periselectivity in the thermal reaction of
ketenes with dienes.I'' Although the Diels-Alder products
[*I Dr. M. Schmittel, DipLChem. H. von Seggern
Institut fur Organische Chemie und Biochemie der Universitat
Albertstrasse 21, W-7800 Freiburg (FRG)
[**I Electron Transfer Catalyzed Reactions, Part 1. This work was supported
by the Deutsche Forschungsgemeinchaft, the Land Baden-Wurttemberg,
the Wissenschaftliche Gesellschaft Freiburg, and the Fonds der Chemischen Industrie (H.v.S.J.We thank Prof. Dr. C. Riichardt for continued
support of our studies and R. Burrh and C. Wohrle for help with the
preparative work. Thanks are also due to Prof. Dr. H . Fritz and Dr. D .
Hunkler for recording the 'H-NMR-NOE difference spectra and for help
with their interpretation.
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0570-0833/91/0808-0999 $3.50+.25/0
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stereoselective, thein, carbene, alkynes, couplings, coordinated, isomerization, cyclopropenes, complexes, tungsten, vinylcarbene, ligand
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