Structural Studies of Diethylphenylphosphonite-Transition Metal Complexes

The synthesis and spectral properties of several tetrakis (diethylphenylphosphonite) transition metal complexes are reported. The crystal structures of the hydrido complexes H2Fe((C6H5)P(OC2H5)2)4 and HCo((C6H5)P(OC2H5)2)4 have been determined. The phosphorus ligands are disposed nearly tetrahedrally about the metal atoms, with the hydrogen ligands occupying faces of the tetrahedra. Infrared and n.m.r. studies of the hydrido complexes in methylcyclohexane solution indicate that the molecules are stereochemically non-rigid. The classical coordination structures used in discussing rearrangements of five- and six-coordinate complexes (octahedron, square pyramid, and trigonal bipyramid) are found to be inadequate in the discussion of the present complexes. A structure based on a tetrahedral skeleton of phosphorus atoms is presented as an alternative.