Chemistry of polynuclear compounds. Part XIII. The preparation and some reactions of dodecacarbonyltriosmium

Abstract

Dodecacarbonyltriosmium, Os₃(CO)₁₂, and a series of related trimeric derivatives, Os₃(CO)₁₀XY (X = H, Y = H, OH, or OMe; X = Y = OMe), have been prepared from the reaction of osmium tetroxide in methanol with carbon monoxide at moderate pressures and temperatures. Mass spectral, i.r. and n.m.r. data support a cyclic configuration for the compounds Os₃(CO)₁₀XY, possibly involving an OsOs double bond. The reactions of Os₃(CO)₁₂ with base and with halogens have been investigated and the compounds H₂Os₄(CO)₁₃, H₄Os₄(CO)₁₂, HOs₃(CO)₁₀(OH), and Os₃(CO)₁₂X₂(X = Cl, Br, or I) isolated. The tetranuclear hydrides are similar to H₂Ru₄(CO)₁₃ and β-H₄Ru₄(CO)₁₂ reported previously. I.r. and mass spectral data for Os₃(CO)₁₂X₂ favour a linear arrangement (X–Os–Os–Os–X) of the three metal atoms with an overall molecular symmetry D_4h. Mass spectral evidence for the formation of Os₂(CO)₈X₂ and Os₂(CO)₆X₄ from the thermal decomposition of Os₃(CO)₁₂X₂ is offered.