Chain and ring assemblies of diosmium sawhorse complexes linked by 1,1'-bis(diphenylphosphino)ferrocene ligands

Three complexes containing diosmium(I) sawhorse units have been synthesized by reactions of 1,1'-bis(diphenylphosphino)ferrocene (dppf) with [Os2(µ-acetate)2(CO)6], [Os2(µ-acetate)2(CO)4(κ1-dppf)2] (1), [(µ-dppf){Os2(µ-acetate)2(CO)4(κ1-dppf)}2] (2), and [(µ-dppf)3{Os2(µ-acetate)2(CO)4}3] (3). In all three cases, the axial CO ligands of the diosmium starting material were replaced by axial dppf ligands. Both 1 and 2 contain two monodentate dppf ligands. In each molecule of 2, there is also one bidentate dppf ligand that serves as a bridge between two Os2 sawhorse units. Complex 3 has a unique cyclic molecular structure involving three sawhorse units connected by three bidentate bridging dppf ligands with alternating sawhorse and dppf moieties forming a ring. Complexes 2 and 3 were characterized by X-ray crystallography.