Correlation of the hydrogénation catalytic activity of dinuclear complexes of rhodium(I) with the formation of carbonyl-bridged complexes

Abstract

Methanolic solutions of the dinuclear cationic complexes of rhodium(I), [Rh2(μ-X)(CO)2(Ph2ECH2EPh2)2]+ (X = Cl, Br; E = P, As) and iridium(I), [Ir2Cl(CO)3(Ph2PCH2PPh2)2], are each active catalysts for the hydrogenation of alkynes to alkenes, and alkenes to alkanes. Neutral complexes with pseudohalide ligands have also been investigated but only the cyano-complex [Rh2(CN)2(CO)2(Ph2PCH2PPh2)2], and the arsine analog, are of significant catalytic activity. Only those complexes which reversibly form bridged complexes with ligands such as CO are also catalytically active.Similar complexes with dithioether ligands are not efficient catalysts under the conditions tested.