Reactions of H2Os3(CO)10 with triallylboranes: formation of novel triosmium boron-containing olefin clusters

Abstract

H₂Os₃(CO)₁₀ (1) reacts with triallylborane B(CH₂CHCH₂)₃ at 25 °C to form the cluster [Os₃(CO)₁₀(μ-η²:η²-trans-MeHCCH)₂BC₃H₇] (2). Reaction of 1 with a mixture of triallylborane–trimethallylborane (1 : 3) gives a mixture of clusters 2, [Os₃(CO)₁₀(μ-η²:η²-Me₂CCH)₂BC₃H₇] (3) and {Os₃(CO)₁₀[μ-η²:η²-(trans-MeCHCH)(Me₂CCH)]BC₃H₇} (4). The reaction results in the B–C bond cleavage and the isomerization of two allyl fragments into substituted vinyl groups coordinated to the osmium atoms in an η²-fashion, and reduction of the third fragment to a propyl group. The mechanism of the reaction is discussed based on isotope labelling and influence of the boron substituent ligand on the reaction path and product identity. Clusters 2, 3, 4 are characterized by spectroscopic means as well as by X-ray studies.