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

Abstract

Detailed herein are synthetic, spectroscopic and structural studies on trisisocyanide cobalt halide complexes featuring the encumbering m-terphenyl isocyanide CNAr Mes2 (Mes = 2,4,6-Me 3C 6H 3). Addition of CNAr Mes2 to CoI 2 in a 3:1 molar ratio provides the mononuclear complex, CoI 2(CNAr Mes2) 3, which can be oxidized to six-coordinate CoI 3(CNAr Mes2) 3 upon treatment with 0.5 equivalents of I 2. Contrastingly, addition of CNAr Mes2 to CoBr 2 provided the dinuclear complex Br 2Co(μ 2-Br) 2Co(CNAr Mes2) 3 irrespective of the molar ratios employed. FTIR analysis on these Co(II) and Co(III) complexes is used to assess the relative π-basicities of the cobalt centers toward the CNAr Mes2 ligands. Treatment of CoX 2 (X = Cl, Br and I) with three CNAr Mes2 ligands followed by the addition of granulated Zn provides the pseudo-tetrahedral complexes XCo(CNAr Mes2) 3. FTIR, magnetic and X-ray crystallographic studies are used to determine both the ground state electronic structure and relative π-basicities of these complexes.