Preparation and properties of cobalt(II) phosphine complexes containing nitro and nitrosyl ligands

Abstract

Reactions of the tertiary phosphines PMe 3, PEt 3, PMe 2Ph, PMePh 2 and PPh 3 with Co(NO 2) 2 are described. For PMe 3 and PMe 2Ph, five-coordinate Co(NO 2) 2(PR 3) 3 complexes ( 1, 2) are isolated. With PEt 3, only Co(NO)(NO 2) 2(PEt 3) 2 ( 3) is obtained, whereas the Co(NO)(NO 2) 2(PMe 3) 2 ( 4) and Co(NO)(NO 2) 2(PMe 2Ph) 2 ( 5) analogs result from the reaction of 1 and 2 with NO gas. From EPR measurements, the electronic structures of 1 and 2 are found to correspond to low-spin d 7 square-pyramidal complexes in the solid state. Compounds 3, 4 and 5 are pseudo-octahedral Co(III) species containing three different nitrogen oxide ligands, namely NO, O-bonded NO 2 and N-bonded NO 2. The reactions of 1 and 2 with CO are solvent dependent: in methanol Co(NO)(CO)(PMe 3) 2 is obtained, but in toluene a mixture of 5 and Co(NO) 2(NO 2)(PMe 2Ph) precipitates. Co(NO)(NO 2) 2(PEt 3) 2 reacts with O 2 to form the cobalt(II) complex Co(NO 3) 2(OPEt 3) 2 shown by X-ray diffraction to be a distorted octahedron with bidentate nitrate ligands and two OPEt 3 ligands in cis positions.