Reactions of [Os₃(μ-H)₂(CO)₁₀] with diazo-compounds: Structural characterization of [Os₃(μ-H)(CO)₁₀(μ-NHNCPh₂)] and [Os₃(μ-H)(CO)₁₀(μ-NHNCPhMe)]

The unsaturated cluster [OS₃H₂(CO)₁₀] reacts with diazo-compounds N₂CR¹R² to give complexes of the form [OS₃(μ-H)(CO)₁₀(μ-NHNCR¹R²)] [R¹ = R² = Ph(1); R^l = Ph, R² = Me(2); R¹ = Ph, R² = H(3); and R¹ = R² = Me(4)]. Compound (4) reverts to [Os₃H₂(CO)₁₀] in solution at 20 °C; a mechanism for the decomposition of complex (4) is proposed. Complexes (1)-(3) are stable in solution and the structures of [Os₃(μ-H)(CO)₁₀(μ-NHNCPh₂)] (1) and [Os₃(μ-H)(CO)₁₀(μ-NHNCPhMe)] (2) in the solid state have been confirmed by single-crystal X-ray analyses. Both complexes crystallise in the monoclinic space group P2₁/c with Z = 4, and a = 13.645(7), b = 11.948(8), c = 16.784(11) Å, β = 101.36(3)° for (1) and a = 17.020(8), b = 9.181(3), c = 16.594(7), Å, and β = 113.70(2)° for (2). The structures have been solved by a combination of direct methods and Fourier techniques, and refined by blocked full-matrix least squares to R = 0.079 for 2 712 observed intensities (1) and R = 0.050 for 2 375 intensities (2). In both structures the Os atoms define an isosceles triangle the short edge of which is bridged by an N atom of the NHNCR¹R² ligand and by the hydride. Spectroscopic data for (2) indicate the presence of two isomers in solution.