Asymmetric diosmium sawhorse complexes.

Three asymmetric diosmium(I) carbonyl sawhorse complexes have been prepared by microwave heating. One of these complexes is of the type Os(μ-OCR)(μ-OCR')(CO)L, with two different bridging carboxylate ligands, while the other two complexes are of the type Os(μ-OCR)(CO)L, with one axial CO ligand and one axial phosphane ligand. The mixed carboxylate complex Os(μ-acetate)(μ-propionate)(CO)[P(p-tolyl)], (1), was prepared by heating Os(CO) with a mixture of acetic and propionic acids, isolating Os(μ-acetate)(μ-propionate)(CO), and then replacing two CO ligands with two phosphane ligands.