Hydrocarbon complexes of iron, ruthenium, and osmium. Part IX. Cycloheptadienyl- and cycloheptatrienyl-carbonylosmium complexes

Abstract

Treatment of the compounds [Os(MR₃)₂(CO)₄](MR₃= SiMe₃, Sime₂Ph, or GeMe₃) or [{Os(MR₃)(CO)₄}₂](MR₃= SiMe₃ or SiEt₃) with cycloheptatriene or cyclohepta-1,3-diene yields cycloheptadienyl complexes [Os(MR₃)(CO)₂(1–5-η-C₇H₉)] as major products, and bridging cycloheptatrienyl complexes [Os₂(MR₃)(CO)₅-(1–2,3–4-η : 5–7-η-C₇H₇)]. In their i.r. spectra the cycloheptadienyl complexes exhibit three carbonyl stretching bands; and temperature-dependent ¹H n.m.r spectra, attributed to restricted rotation about the osmiumcy–cloheptadienyl bond, allowing the existence of conformatiional isomers which interconvert rapidly at ambient temperature, but are observable on the n.m.r. time scale at low temperatures. Some reactions of the complex [Os(SiMe₃)(CO)₂(1–5-η-C₇H₉)] have been stuied.