New paramagnetic Re(II) compounds with nitrile and cyanide ligands prepared by homolytic scission of dirhenium complexes

Abstract

The preparation and characterization of three new paramagnetic complexes of the 17-electron Re^II 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 Re₂^II,^II starting materials are viable precursors for producing unusual mononuclear Re^II complexes.