Nickel, Cobalt, and Copper Complexes of o-Benzenediselenolate: Synthesis and Structural and Magnetic Properties

Abstract

The o-benzenediselenolate (bds2-, 1b) ligand is conveniently prepared by sodium borohydride reduction of poly(o-phenylene diselenide), which was readily synthesized from o-dibromobenzene and sodium diselenide. The bds2- species was characterized by reaction with thiophosgene to give the known 4,5-benzo-1,3-diselenole-2-thione (3) and with the chlorides of nickel, cobalt, and copper to give new diselenolenes isolated as tetra-n-butylammonium salts. The new complexes were characterized by elemental analysis, cyclic voltammetry, electronic spectra, static magnetic susceptibility, electron spin resonance (ESR) spectroscopy, and X-ray diffraction, and, where possible, the properties of the bds complexes were compared to those of the sulfur analogue (bdt2-, 1a) or the mixed-sulfur-selenium analogue (1c). The intense features of the electronic spectra of the three bds complexes are observed at energies lower than those reported for the bdt complexes. The magnetic moments of the Ni– and Co–bds complexes are 1.94 and 3.43 μB, respectively; both are slightly larger than those reported for the bdt analogues. Polycrystalline samples of the Ni(bds)2- complex have axial ESR signals, and the principal components of the g tensor are reported. The temperature dependence of the g values and differential scanning calorimetry provide evidence for a phase transition near 167 K. The ESR spectra of polycrystalline samples of Co(bds)2- at low temperatures reveal the half-field resonance, which indicates that the electronic ground state is a triplet. The principal components of the g tensors for the Ni– and Co–bds complexes are larger than for the corresponding bdt complexes, indicating a larger spin-orbit interaction in the heavier chalcogen systems. (n-C4H9)4N+Ni(bds)2-, C28H44NSe4Ni, is an orthorhombic crystal of space group Pbc21 with a = 9.904 (3) Å, b = 16.954 (5) Å, c = 19.106 (6) Å, V = 3208.1 Å3, and Z = 4. The structure was solved by Patterson and difference-Fourier syntheses and reveals a mixed-stack array of cation and anion, precluding cooperative magnetic interactions, as observed in the Curie law behavior of the susceptibility and in the resolved anisotropic g-tensor ESR spectral envelope. X-ray photographic studies reveal that the Co and Cu bds complexes are isomorphous to the Ni complex. © 1987, American Chemical Society. All rights reserved.