Inorg. Chem. 1993, 32, 1539-1540 1539
Synthesis of Heterobimetallic Allene Complexes
Iuan-Yuan Wu, Tian-Wen Tseng, Chun-Ting Chen, Ming-Chu Cheng, YingChih Lin,’ and Yu Wang Department of Chemistry, National Taiwan University, Taipei, Taiwan 10764, Republic of China
Received October 15, 1992
The first dinuclear complex containing a four-electron p-q2,q2- allene ligand was synthesized from the reaction of allene with [Cp(C0)2M0]2 (Cp = q5-C5H5) and was reported in 1977.1 Thereafter, a number of complexes of this type were prepared,2 notably by photolysis of dinuclear complexes with a bridging cyclopropylidene ligand.2b,c Several dinuclear and trinuclear metal complexes containing allenyl ligands in various bonding modes have been prepared by initially using a propargyl ligand as a t e m ~ l a t e . ~ Despite these and other report^,^ methods that lead to formation of a heterodinuclar p-q2,q2-allene complex are still l a ~ k i n g . ~ In exploring the chemistry of a tungsten @-(chlo- rocarbony1)allylic complex
Cp(C0)2W(q3-CH2C(COCl)CH2)
(la)? we prepared several dinuclear complexes by replacing the C1 atom with another metal group and found photolysis of such complexes provided a systematic approach to the dinuclear p+,q2- allene complexes. Herein, we report several complexes synthesized via this approach and their characterization.
The reaction of
Cp(CO)2W(q3-CH2C(COCl)CH2)
(la)6 with CP(CO)~W- in THF resulted in the formation of a homonuclear complex Cp( CO) 2W [ p-q3,q1-CH2C( CO)CH2] W(C0) 3Cp (2a). Heteronuclear analoguesCp(C0)2M(p-q3,q1-CH2C(CO)CH2)M’
(2b, M = Mo, M’ = W(CO)3Cp; 2c, M = W, M‘ = Fe(C0)zCp;
2d, M = W, M’ = Re(CO)5) were prepared similarly. However, attempts to prepare similar complexes using the Cp(C0)3Mo- anion were unsuccessful. We believe that metal anions with weak nucleophilicity7 may not be applicable for the preparation of 2 employing this synthetic strategy. On the basis of the EAN rule, the two metal centers in 2 bridged by a p-q3,q’-/3-carbonylallylic ligand should have no M-M bond. Complexes 2 were charac- terized through a combination of microanalytical data and IR, IH NMR, and I3C NMR spectroscopy.8 For example, in the ‘H NMR spectrum of 2a at room temperature, the two inequivalent Cp groups displayed a sharp resonance and a broad resonance and the allylic syn and anti protons appeared as two broad resonances at 6 2.76 and 1.38, respectively. These broad resonances are due to the fluxional behavior of the endo and exo
configurations of the allylic group. At 240 K, the two broad resonances at 6 2.76 and 1.38 of 2a were resolved into two sets of allylic protons at 6 2.78, 1.16 and 2.68, 1.58,8 assignable to those of the endo and exo isomers, respectively.
Photolysis of complexes 2a-c with UV irradiation in benzene resulted in the loss of two CO ligands and afforded the dinuclear
( I ) Chisholm, M. H.; Rankel, L. A,; Bailey, W. I.; Cotton, F. A.; Murillo, C. A. J . Am. Chem. SOC. 1977, 99, 1261.
(2) (a) Lewis, L. N.; Huffmann, J. C.; Caulton, K. G. J . Am. Chem. SOC.
1980, 102, 403. (b) Casey, C. P.; Austin, E. A. Organometallics 1986,
5 , 584. (c) Casey, C. P.; Austin, E. A. J . Am. Chem. SOC. 1988,110, 7106. (d) Hoel, E. L.; Ansell, G. B.; Leta, S . Organometallics 1986,
5, 585.
(3) (a) Wojcicki, A.; Shuchart, C. E. Coord. Chem. Reu. 1990,105,35. (b) Young, G. H.; Raphael, M. V.; Wojcicki, A,; Calligaris, M.; Nardin, G.; Bresciani-Pahor, N. Organometallics 1991, 10, 1934-1945. (4) Jones, M. D.; Kemmitt, R. D. W. Adu. Organomet. Chem. 1987, 27,
279.
(5) A Ni-W complex previously thought to have a p-$$-allene ligand was found to have a pu-$,q’ structure: (a) Chetcuti, M. J.; Fanwick, P. E.; McDonald, S. R.; Rath, N. N. Organometallics 1991, 10, 1551. (b) Chetcuti, M. J.; McDonald, S. R.; Rath, N. N. Organometallics 1989, 8, 2077.
(6) Tseng, T. W.; Wu, I. Y.; Lin, Y. C.; Chen, C. T.; Chen, M. C.; Tsai, Y. J.; Chen, M. C.; Wang, Y. Organometallics 1991, 10, 43. (7) King, R. B. Acc. Chem. Res. 1970, 3, 417.
(8) Preparations and spectroscopic data of these complexes are given in the supplementary material.
0020-1669/93/1332-1539$04.00/0
allene complexes C p ( C 0 ) 2 M ( r - q 2 , q 2 - C H 2 ~ ~ H 2 ) M ” (4a,
M = W, M” = Fe(C0)Cp); see Scheme I. Complexes 4 were characterized by spectroscopic methods. In addition, the mo- lecular structure of 4c was determined by an X-ray diffraction a n a l y ~ i s . ~ In each unit cell, there are two independent molecules which are an enantiomeric pair and differ only slightly in their bond lengths and angles. Figure 1 shows one of the molecules. As expected, the C j unit is nonlinear with a C-C-C bond angle of 140(4)”. The three-carbon allene unit sits above the W-Fe axis in a criss-cross arrangement. This geometry allows interaction of one ?r-bond of the allene with the W center and of the second *-bond of the allene with the Fe center. With such a structure, the heteronuclear system should display two sets of inequivalent geminal protons, Le. proximal and distal with respect to the M-M’ bond. Indeed, in the
IH
NMR spectra of heteronuclear allene complexes, four allene protons displayed four multiplet resonances (6 4.50, 3.02, 2.66, 2.40 for 4c and 6 4.22, 3.69, 2.67, 2.45 for 4b). In contrast, in the homonuclear system,’ there is a C2 axis passing through the center carbon of the allene ligand and the midpoint of the M-M vector. Therefore, in theIH
NMR spectrum of 4a, a deceptively simple triplet pattern for the methylene protons was observed.In the photolytic decarbonylation reactions of 2a and 2b, an intermediate formulated as Cp(CO)2M(p-q3,ql-CH,CCH2)- W(CO)3Cp (3a, M = W; 3b, M = Mo) was observed. Pre- sumably, the two metal centers in 3 are bridged by a q3,ql-allylic ligand as shown in the Scheme I.lo Complexes 3a and 3b were observed but not isolated.* Interestingly, for rhenium complex 2d, only one decarbonylation was attained and the complex
Cp(C0)2W(p-q3,ql-CH2CCH2)Re(CO)5
(3) was isolated in 45% yield. In theIH
NMR spectrum of 3d, the resonances of the allylic protons at 6 3.09, 1.67 are typical for syn/anti resonances of an allylic system. The mass spectrum of3d
displayed parent peaks as well as fragmentationsdue to loss of CO.’ W-Re metal- metal bonds have been observed in several complexes.11 Reasons for no further decarbonylation of 3d are not clear.M = W, M” = W(CO)2Cp; 4b, M = Mo, M” = W(CO)2Cp; 4c,
(9) Yellow crystals of 4c were grown by slow diffusion of n-hexane into a dichloromethane solution of 4c at 4 OC. Crystal data: space group X-ray data were collected at r w m temperature on an Enraf-Nonius CAD4diffractometer using graphite-monochromated Mo K a radiation. A total of 2205 reflections were collected with use of the 0-28 scanning technique between 2.0 and 49.9’ in 28. A total of 1553 reflections with
I > 241) were used in the full-matrix least-squares refinement. The structure was solved by using heavy-atom methods with the NRCC computing package. The final values of the agreement indices were R = 0.062, R , = 0.060, and GOF = 2.20.
(10) Conole, G.; Henrick, K.; McPartlin, M.; Horton, A. D.; Mays, M. J.; Sappa, E. J . Chem. SOC.. Dalton Trans. 1990, 2367.
(1 I ) (a) Fontana, S.; Orama, 0.; Fischer, E. 0.; Schubert, U.; Kreissl, F. R .
J . Organomet. Chem. 1978,149, C57. (b) Ginley, D. S.; Wrighton, M. S . J . Am. Chem. SOC. 1975, 97, 4908.
(12) Yellow crystals of 5 were grown by slow diffusion of n-hexane into a dichloromethane solution of 5 at 4 OC. Crystal data: space group PZI/
c, a = 8.681(3) A, b = 13.420(5) A, c = 17.630(9) A, 6 = 103.48(4)O,
Z = 4. X-ray data were collected at r w m temperature on an Enraf- Nonius CAD4 diffractometer using graphite-monochromated Mo K a radiation. A total of 3514 reflections werecollected with useof thew-28 scanning technique between 2.0 and 49.9O in 28. A total of 2408 reflections with Z > 241) were used in the full-matrix least-squares refinement. The structure was solved by using heavy-atom methods with the NRCC computing package. The final values of the agreement indices were R = 0.044, R , = 0.032, and GOF = 2.43.
P212121, u = 7.606(2) A, b = 12.333(6) A, c 31.072(7) A, Z = 4.
0 1993 American Chemical Society
Downloaded by NATIONAL TAIWAN UNIV on August 10, 2009
1540 Inorganic Chemistry, Vol. 32, No. 9, 1993 Scheme I Communications 4 a , M = W 4b, M = MO I a , M = W 1 b, M = Mo C28 2a, M = W; M = CP(CO)~W 2c, M = W; M = Cp(CO)pFe 2d, M = W; M' = (CO)&s 2b, M = Mo; M' = c p ( C 0 ) ~ W
i
Hi 5 enddexo Figure 1. O R T E P drawing of C p ( C 0 ) 2 W ( r - q 2 , q 2 - C H 2 = C = CH2)Fe(CO)Cp(4c) with thermal ellipsoids shownat the 50% probability level. Selected bond distances(A)
and bond angles (deg) are as follows: Fe-C(12B), 1.91(4); Fe-C(13B), 2.08(5); W-C(l l B ) , 2.34(4); W-C(I2B),2.07(4);C(12B)-C(13B), 1.34(6);C(llB)-C(12B), 1.45(6); C( 1 lB)-C( 12B)-C( 13B), 140(4).Treatment of 2c with HBF4 resulted in the formation of a
cationicenonecomplex
[Cp(C0)2W(~-v4,+CH2=C(CH3)CO)-
Fe(CO)2Cp]BF4 (5).8 Complex 5 in solution gave a mixture of endolexo isomers with a ratio of 6.4: 1. The structure of 5 was also confirmed by X-ray diffraction analysis.12 As shown in Figure 2, the enone group adopts an s-cis configuration and is in an endo conformation with respect to the Cp group.13 The $-coordination of the enone group is revealed by the one W-O and three W-C bonding distances. A slightly longer W-C(2) separation of 2.49( 1)
A
as compared to the other W-C separations (2.24( 1) and 2.28( 1)A)
may be attributed to the steric effect of the iron moiety and to a relatively short W-0(3) distance of 2.141(7)A.
For a cationic molybdenum butadiene complex,I4 four isomers (endolexo and cisltrans) have been observed at low temperature. (13) (a) Takats, J.; Kurczynski, L. J. Am. Chem. SOC. 1974, 96, 932. (b) Takats, J.; Kurczynski, L. Inorg. Chem. 1976, I S , 3140. (c) Dorf, U.; Engel, K.; Erker, G. Organometallics 1983,2,462. (d) Tachikawa, M.; Shapley, J. R.; Haltiwanger, R.; Pierpont, C. G. J. Am. Chem. SOC.
1976,98,4651. ( e ) Vong, W. J.;Peng,S. M.; Liu, R. S. Organometallics
1990, 9, 2187.
(14) Faller, J. M.; Rosan, A. M. J . Am. Chem. SOC. 1977, 99, 4858.
3a, M = W M = Cp(CO)3W 3d, M = W; M = (CO)& 3b, M = Mo; M' = Cp(CO)3W 4c 08 Figure 2. O R T E P drawing of Cp(C0)2W(p-q4,q1-CH2=C(CH3)- CH=O)Fe(CO)$p (5) with thermal ellipsoids shown at the 50% probability level. Selected bond distances (A) and bond angles (deg) are as follows: Fe-C(2), 1.946(1); W - O ( l ) , 2.141(7); W-C(2), 2.49(1); W-C(3), 2.28(1); W-C(4), 2.24(1); C(2)-0(1), 1.32(1); C(2)-C(3), 1.43(2); C(3)-C(4), 1.42(2); C(3)-C(5), 1.49(2); C(2)-C(3)-C(4), 115(1); O(l)-C(2)-C(3), 110.7(9); C(4)-C(3)-C(5), 121(1). In our case, the s-trans configuration was not observed probably due to the steric bulk of the metal moiety.
Using B-(chlorocarbony1)allylic metal complexes as starting materials, we have demonstrated the preparation of a hetero- nuclear complex with a j3-(carbonyl)allylic bridging ligand. Photolysis of this product led efficiently to the heteronuclear p-v2,q2-allene complex. Reactivity of allene complexes with heteronuclear metal centers is currently under investigation.
Acknowledgment. We are grateful for financial support of this work by the National Science Council of the Republic of China.
Supplementary Material Available: A textual presentation of the syntheses and spectroscopic data for 2a, 2b, Zc, M , 3b, 4b, 4c, and 5 and tables of X-ray crystallographic data, positional parameters, anisotropic thermal parameters, and selected bond distances and angles for 4c and
5 (1 1 pages). Ordering information is given on any current masthead page.
Downloaded by NATIONAL TAIWAN UNIV on August 10, 2009
