J . A m . Chem. SOC.1987, 109, 910-911
910 cleophilic additions to alkyl ketones.I8
c 81 C 71
Acknowledgment. We are grateful to the National Institutes of Health, the Harris Corporation, and the National Science Foundation San Diego Supercomputer Center for financial support of this research. (18) For different interpretations, see: Cheung, C. K.; Tseng, L. T.; Lin, M.-H.; Srivastava, S.; le Noble, W. J. J . Am. Chem. SOC.1986, 108, 1598. Danishefsky, S.;Lange, M. E. J . Org. Chem. 1985, 50, 3673. Fraser, R. R., unpublished results.
Synthesis and Structure of a Diiron Divinylidene Complex Formed by Oxidative Carbon-Carbon Coupling Ramnath S. Iyer and John P. Selegue* Department of Chemistry, University of Kentucky Lexington, Kentucky 40506-0055 Received June 27, 1986 Revised Manuscript Received November 15, 1986 Transition-metal vinylidene complexes and higher metallacumulenes' are carbon-rich species which model reactive intermediates formed from surface carbides in heterogeneously catalyzed C O reduction and acetylene conversion reactionsS2 Of particular interest are reactions in which carbon-carbon bonds are formed, modeling hydrocarbon chain growth or graphite layer formation. We report here an oxidatively induced coupling of iron vinylidene complexes. On the basis of Gladysz's conversion of methylene to formaldehyde on r h e n i ~ mwe , ~ anticipated that reactions of cationic iron vinylidene complexes4 [Fe(C=CR,)(PR,),(Cp)]+ with oxygen atom donors would lead to ketene complexes [Fe(O=C= CR,) (PR,),(Cp)]+. However, [Fe( C=CMe,)(dppe) (Cp)]' does not react with either trimethylamine N-oxide or iodosobenzene, and [Fe(C=CHMe)(dppe)(Cp)]+ (1) is simply deprotonated by Me3N0., The reaction of [Fe(C=CHMe)(dppe)(Cp)] [BF,] (1, 0.39 g, 0.60 mmol) with iodosobenzene6 (1.2 g, 5.45 mmol) in acetonitrile (20 mL) under nitrogen at room temperature for 4 h, followed by evaporation and recrystallization of the residue from dichloromethane/ethyl ether, gave deep red-purple crystals of [Fe2(p-C4Mez)(dppe),(Cp)2][BF,], (2,0.30 g, 77%).' The most striking feature of the X-ray crystal structure8 of 2 (Figure 1)
Figure 1. O R T E P ~ O plot of the central portion of the cation in [Fe2(pC4Me2)(dppe)2(Cp)2] [BF,], showing 50% probability ellipsoids. Phenyl groups are abbreviated for clarity. Important distances (A) and angles: Fel-C1 1.746 (9), Fel-P1 2.222 (3), Fel-P2 2.223 (3), Fe2-C2 1.766 (9), Fe2-P3 2.207 (3), Fe2-P4 2.201 (3), C1-C3 1.33 ( l ) , C3-C4 1.50 ( I ) , C3
