Reactions of [Os3H2(CO)9(PR3)], PR3= PPh3, PPh2Et, or P(OMe)3, with nucleophiles

Abstract

The vinyl complexes [Os₃H(CO)₉L(CHCH₂)][L = PPh₂Et, P(OMe)₃], and PPh₃] are formed by reacting the [Os₃H₂(CO)₉L] species with acetylene, and exist in two isomeric forms. Vinyl complexes are also obtained by reacting [Os₃H₂(CO)₉L](L = PPh₂Et and PPh₃) with ethylene. Intermediate ethylene adducts were also observed. In these adducts, and also those of MeNC, the substrate is bound to the phosphine-substituted osmium atom, with the C₂H₄ and MeNC ligands in equatorial and axial sites respectively. Thermolysis of [Os₃H(CO)₉(PPh₂Et)(CHCH₂)] affords [Os₃H₂(CO)₈(PPh₂Et)(CCH₂)] in high yield. The latter complex reacts with hydrogen to form [Os₃H₃(CO)₈(PPh₂Et)(CCH₃)]. Nucleophilic addition to [Os₃H(CO)₉L] appears to be orbitally controlled.