The protonation of ruthenium- and rhodium-bridged carboxylates and their use as homogeneous hydrogenation catalysts for unsaturated substances

Abstract

The protonation of rhodium(II) acetate by non-complexing, non-oxidising acids such as fluoroboric acid gives the green rhodium(II) cation Rh⁴⁺ ₂. The interaction with triphenylphosphine and carbon monoxide lead to the complexes Rh(PPh₃)₃BF₄ and Rh(CO)(PPh₃)₃BF₄. The new ruthenium(II) acetate Ru₂(OCOMe)₄ and its adducts with triphenylphosphine and pyridine have been characterised. The methanolic fluoroboric acid solutions of Rh^II and Ru^II acetates and of Ru₂(OAc)₄Cl, in the presence of triphenylphosphine, are active catalysts for the homogeneous hydrogenation of alkenes, alkynes, and other unsaturated substances.