Cobaloximes with Bis(thiophenyl)glyoxime: Synthesis and Structure−Property Relationship Study

Alkyl and non-alkyl cobaloximes with bis(thiophenyl)glyoxime, X/RCo(dSPhgH)2Py (X = Cl, R = Me, Et, Pr, Bu, Bn) have been synthesized and characterized for the first time. The X-ray structures of the complexes ClCo(dSPhgH)2Py, EtCo(dSPhgH)2Py, and BuCo(dSPhgH)2Py are reported. The orientation of SPh groups with respect to the dioxime plane varies with the steric bulk of the axial ligand and affects the NMR chemical shifts. The cis and trans influence has been studied by 1H NMR, 13C NMR, and X-ray diffraction. The steric cis influence of the equatorial thiodioxime affects the Co−C bond reactivity in their cobaloxime complexes. The molecular oxygen insertion into the Co−C bond and steric cis influence are related to each, and both follow the same order, dmestgH ≫ dpgH > chgH > dSPhgH ≥ dmgH > gH. A cyclic voltammetry study shows that the reductions, Co(III)/Co(II) and Co(II)/Co(I), are easier in ClCo(dSPhgH)2Py as compared to other chlorocobaloximes (gH, dmgH, dpgH, mestgH).