Electron spin resonance and bulk paramagnetism studies of some diarylbis(diethylphenylphosphine)cobalt(II) complexes

Abstract

Magnetic susceptibilities and measurements of the e.s.r. and electronic spectra are reported for the low-spin planar complexes [Ar₂(PEt₂Ph)₂Co^II](Ar = mesityl, 2-methylnaphthyl, pentafluorophenyl and pentachlorophenyl). Single-crystal measurements on the mesityl compound show that the magnetic ellipsoid has approximately axial symmetry with the unique axis lying in the co-ordination plane. A configuration energy scheme is derived from this result and places the unpaired electron in the d_z² orbital. Powder results for the other members of the series have been interpreted similarly. The resultant configuration energies within the series are discussed in terms of the bonding properties of the ligands involved.