Synthesis and structures of (3-methyl-2-pyridyl)diphenylphosphane derivatives of metal clusters

An unsymmetric bidentate ligand (3-methyl-2-pyridyl)diphenylphosphane (P(Mepy)Ph2) is able to react with various tetranuclear transition metal clusters such as HRuCo3(CO)12, HRuRh3(CO)12 and Rh4(CO)12. The synthesis and crystal structures of HRuCo3(CO)10(P(Mepy)Ph2) (1), HRuRh3(CO)10(P(Mepy)Ph2) (2), RuRh2(CO)9(P(Mepy)Ph) (3) and Rh6(CO)14(P(Mepy)Ph2) (4) are described. In 1, 2 and 4 the phosphane ligand replaces the carbonyls and acts as a bridging bidentate P–N group. The formation of 3 includes degradation of both the metal cluster core and the ligand itself. One of the P–C bonds in the ligand is cleaved and the ligand caps a metal triangle with a bridging phosphido group together with the nitrogen donor. The reaction between dinuclear Rh2(CO)4Cl2 and P(Mepy)Ph2 gives a binuclear Rh2(μ-CO)Cl2(P(Mepy)Ph2)2 (5) with bridging ligands in a head-to-tail arrangement. The crystal structure is also given.