Reactions of (η-allyl)tricarbonylchlororuthenium(II) with hydrogen and unsaturated substrates: catalytic hydrogenation and isomerisation of alkenes

Abstract

The complex [RuCl(C₃H₅)(CO)₃], (I), reacts with hydrogen to give polynuclear ‘alkyloxycarbene’ derivatives arising from intramolecular carbonylation of the alkyl groups derived from hydrogenation and isomerisation of the allyl group. Reactions of (I) with unsaturated substrates such as acrylonitrile (acn), alkynes, butadiene, and acetylenic esters have been studied by i.r. and ¹H n.m.r. techniques. The solids [{RuCl(σ-C₃H₅)(CO)₂(acn)}₂], [{RuCl(OC·CR:CR′·C₃H₅)(CO)₂}₂](R = R′= H; R = H, R′= Ph; and R = R′= Ph), and [RuCl{(C₄H₆)₃-C₃H₅}(CO)₃] have been isolated. In the case of diethyl acetylenedicarboxylate an alkenyl complex of formula [RuCl{C(CO₂Et):CH·C(OEt)O}(CO)₃] has been obtained. Under mild conditions complex (I) is shown to be an effective catalyst for homogeneous hydrogenation of terminal, internal, and cyclic alkenes, and carbonyl compounds. A very fast isomerisation of the substrate occurs during the hydrogenation; the isomerisation takes place also in the absence of hydrogen.