摘要：

A three-dimensional, single-crystal X-ray examination of Co3(CO)9CCH3 has afforded the first detailed structural characterization of a tricyclic Co3(CO)9CY complex which represents the only known class of compounds containing an aliphatic carbon atom triply bridged to three metal atoms. The crystals of Co3(CO)9CCH3 contain two molecules in a reduced triclinic unit cell of symmetry P1 and of lattice parameters a = 8.80 A,b = 9.33 A,c = 12.34 A; α = 93.0°, β = 93.3°, γ = 128.8°. A full-matrix, least-squares refinement of the structure gave an unweighted discrepancy factor of R1 = 11.7%. The molecular configuration ideally possesses C3v symmetry and consists of an apical ethylidyne group, CH3-C<, symmetrically coordinated by three Co-Cσ bonds to a basal Co3-(CO)9 fragment containing three identical Co(CO)3 groups positioned at the corners of an equilateral triangle and bonded to one another by cobalt-cobalt bonds. The salient structural features of Co3(CO)9CCH3 are discussed, and the stereochemistry of the tricyclic Co3C(aliphatic) core is compared with that of the skeletal framework of the tricyclic M3C(carbonyl) fragments embodied in several metal carbonyl complexes. A rationalization of the constrained molecular geometry in terms of bent bonds is given.

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