EPR and Electronic Structural Investigations of a Few Low-Spin Bis(tertiary phosphine) Complexes of Cobalt(II)

Preparation and electronic structural investigations of some low-spin Co(II) complexes of the ligand m-1,2-bis(diphenylphosphino) ethylene (vpp) are reported. Single-crystal EPR studies of [Co(vpp)2Br]BPh4 doped in the corresponding diamagnetic nickel lattice reveals superhyperfine interactions from the in-plane phosphorus nuclei as well as the axial bromine. The EPR results from isotropic, polycrystalline, and single-crystal studies combined with electronic spectral measurements enable us to ascertain the ground state of the unpaired electron. Because of the availability of a sufficient number of bands in the electronic spectra of these complexes, it has been possible to locate all the excited states with reasonable accuracy as borne out by the calculated spin Hamiltonian parameters. Electronic structures of two other related systems-[Co- (dpm)2X]ClO4 and Co(dpe)2X2 (dpm = (diphenylphosphino)methane, dpe = 1,2-bis(diphenylphosphino)ethane, X = Cl, Br, or I)-are also discussed. © 1981, American Chemical Society. All rights reserved.