Synthesis, Characterization and Reactivity of 1,1'-Bis(diphenylphosphino)osmocene: Palladium(II) Complexes and Their Use as Catalysts in the Methoxycarbonylation of Olefins

The synthesis and characterization of 1,1’-bis(diphenylphosphino)osmocene (dppo) is presented. This new ligand forms a variety of palladium(II) complexes showing either k2-P,P or k3-Os,P,P bonding mode. A single-crystal X-ray analysis of [Pd(NCMe)(dppo)](OTf)2 (OTf = trifluoromethanesulfonate) shows the palladium center to be square-planarly coordinated by osmium, two trans phosphorus atoms, and h1-N-MeCN. The complex [Pd(OTs)(dppo)]OTs (OTs = p-toluenesulfonate) is an effective catalyst precursor for the selective methoxycarbonylation of ethylene to methyl propanoate and of styrene to a mixture of methyl 3-phenylpropanoate and methyl 2-phenylpropanoate.