New Paramagnetic Re(II) Compounds with Nitrile and Cyanide Ligands Prepared by Homolytic Scission of Dirhenium Complexes

The preparation and characterization of three new paramagnetic
complexes of the 17-electron ReII ion are reported. The salts [Re(triphos)(CH3CN)3)][X]2, X = [BF4]- (1), [PF6]- (2), and [Et4N][Re(triphos)(CN)3] (3) were prepared by homolytic cleavage of the
Re−Re bond in [Re2(CH3CN)10][BF4]4 or by disruption of the chlorine
bridges in [(triphos)Re(μ-Cl)3Re(triphos)]Cl (1) (triphos = 1,1,1-tris(diphenylphosphino-methyl)ethane) and characterized by single-crystal X-ray diffraction, infrared and 1H NMR spectroscopies, cyclic
voltammetry, and magnetic susceptibility measurements. Compound
2 undergoes reversible reduction and irreversible oxidation
processes while 3 undergoes a reversible reduction, an irreversible
oxidation, and a reversible oxidation. The magnetic susceptibility
data for 2 and 3 exhibit a strong temperature independent
paramagnetic component which is in accord with a highly
anisotropic S = 1/2 magnetic ground state. The results of this study
indicate that dinuclear Re2II,II starting materials are viable precursors
for producing unusual mononuclear ReII complexes.