SYNTHESIS AND CHARACTERIZATION OF NOVEL PHOSPHIDO-SUBSTITUTED AND SELENIDO-SUBSTITUTED RUTHENIUM CARBONYL CLUSTERS

Reaction of the cyclic organophosphorus ligand P4But4 1 with [Ru3(CO)12] or [Ru4H4(CO)12] under forcing conditions yields a number of novel phosphido- and phosphinidene-substituted ruthenium carbonyl clusters. Three products have been structurally characterised in reasonable yield: [Ru4(CO)8(PBut)4] 2, where a square-planar arrangement of four ruthenium atoms is capped above and below the metal-atom plane by two tert-butylphosphinidene ligands, and additionally two mu-phosphinidene ligands bridge two Ru-Ru edges; [Ru5(CO)15(PBut)] 3 in which the five ruthenium atoms adopt a square-pyramidal geometry with the square-basal plane capped by a tertbutylphosphinidene ligand; and [Ru6H2(CO)12(PBut)3] 4, where the six ruthenium atoms define an octahedron with triply-bridging phosphinidene groups capping three triangular faces. Clusters 2 and 4 were isolated from the thermolysis of compound 1 with the tetraruthenium substrate [Ru4H4(CO)12]; cluster 3 is a product of the thermolysis of 1 with [Ru3(CO)12]. In addition, the cluster [Ru4(mu4-Se)2-(CO)8(mu-CO)3] 5 has been isolated by the vacuum pyrolysis of [Ru3(CO)12] with Ph2Se2 at 185-degrees-C. Reaction of this cluster with 1,3-bis(diphenylphosphino)propane (dppp) at room temperature affords the triruthenium phosphine-substituted cluster [Ru3(mu3-Se)2(CO)7(dppp)] 6. The structures of clusters 5 and 6 have also been established by single crystal X-ray analysis.