Syntheses and X-ray Crystal Structures of the Tricobalt Mono(ethylidyne) Clusters Cp*3Co3(µ3-CCH3)(µ3-CO)(µ2-H), Cp*3Co3(µ3-CCH3)(µ3-CNCMe3)(µ2-H), and Cp*3Co3(µ3-CCH3)(µ3-NO)

Cp*3CO3(µ3-CCH3)(µ3-H) (3) reacted with CO to form the 1:1 carbonyl ethylidyne adduct Cp*3Co3(µ3-CCH3)- (µ3-CO) (µ2-H) (5) in 82% yield. Similarly, tery-butyl isocyanide reacted with 3 to form the 1:1 isocyanide ethylidyne adduct Cp*3Co3(µ3-CCH3)(µ3-CNCMe3)(µ2-H) (6) in 87% yield. The reaction of 3 with NO formed the nitrosyl ethylidyne cluster Cp*3Co3(µ3-CCH3)(µ3-NO) (7) in 84% yield. The structures of clusters 5-7 were determined by X-ray crystallography. Each cluster consists of an equilateral triangle of cobalt atoms symmetrically capped on one face by a µ3-CCH3 ligand and capped on the opposite face by a µ3-CO (5), µ3-CNCMe3 (6), or µ3-NO (7) ligand. Line shape analysis of the Cp* peaks in the variable-temperature ¹H NMR spectra of 5 and 6 allowed measurement of the barrier for migration of the hydride ligand between adjacent pairs of cobalt atoms in 5 [ΔG^╪ = 10.3(1) kcal mol^-1] and 6 [ΔG^╪ = 12.2(2) kcal mol^-1]. © 1994, American Chemical Society. All rights reserved.

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Author Ross A. Widenhoefer Chemistry