Pyrazine bridged benzyl dicobaloximes: Competition between π-interaction and steric crowding in crystal structure

Pyrazine (Pz) bridged benzyl dicobaloximes [ArCH2Co(dioxime)2]2-μ-Pz [dioxime = dmgH, dpgH] have been synthesized and characterized with 1H and 13C NMR. The complexes have been synthesized by a simple procedure in one-pot directly from the corresponding benzyl aqua cobaloxime. In the crystal structure of [PhCH2Co(dpgH)2]2-μ-Pz, two cobaloxime units are in eclipsed form whereas they were completely staggered in the reported [EtCo(dpgH)2]2-μ-Pz. This is due to the π–π interaction between the axial benzyl group and phenyl ring of the equatorial dpgH group. Both cis and trans isomer crystallized together in the crystal structure of [PhCH2Co(dpgH)(dmgH)]2-μ-Pz. The cyclic voltammetry study in [PhCH2Co(dioxime)2]2-μ-Pz [dioxime = dmgH, dpgH] shows two cobalt center mixed together due to electron delocalization through pyrazine and behaves like a monocobaloxime and the reduction potentials are much higher than the monocobaloximes.