Structural variation in cobalt halide complexes supported by m-terphenyl isocyanides

Detailed herein are synthetic, spectroscopic and structural studies on trisisocyanide cobalt halide complexes featuring the encumbering m-terphenyl isocyanide CNArMes2 (Mes = 2,4,6-Me3C6H3). Addition of CNArMes2 to CoI2 in a 3:1 molar ratio provides the mononuclear complex, CoI2(CNArMes2)(3), which can be oxidized to six-coordinate CoI3(CNArMes2)(3) upon treatment with 0.5 equivalents of I-2. Contrastingly, addition of CNArMes2 to CoBr2 provided the dinuclear complex Br2Co(mu(2)-Br)(2)Co(CNArMes2)(3) irrespective of the molar ratios employed. FTIR analysis on these Co(II) and Co(III) complexes is used to assess the relative pi-basicities of the cobalt centers toward the CNArMes2 ligands. Treatment of CoX2 (X = Cl, Br and I) with three CNArMes2 ligands followed by the addition of granulated Zn provides the pseudo-tetrahedral complexes XCo(CNArMes2)(3). FTIR, magnetic and X-ray crystallographic studies are used to determine both the ground state electronic structure and relative pi-basicities of these complexes. (C) 2010 Elsevier B. V. All rights reserved.