Pyrazine bridged organodicobaloximes: a convenient one pot synthesis and cis influence studies

Abstract

Twenty six complexes, pyrazine bridged organodicobaloximes of the type RCo(L 2)-pyrazine-Co(L 2)R where R is alkyl group and L is dmgH −/dpgH − have been synthesised. It was found that one could synthesise such complexes in one pot directly from the alkyl(aquo)cobaloximes without converting it to the alkylcobaloxime dimer, as reported in the literature. 1H-NMR studies have revealed that the pyrazine ring protons experience considerably more cis influence than the H α protons of the pyridine in simple alkylcobaloximes. This is presumably because the pyrazine ring protons are in close proximity to two metallabicycles while the H α protons of the simple alkylcobaloximes are influenced by only one metallabicycle. The trends in the Co–C charge transfer transition and N–O, N–O′ frequencies are similar to the alkyl (pyridine) cobaloximes. Low resolution x-ray crystal structure of one of the dicobaloximes, [EtCo(dpgH) 2] μ-Pz indicates that the two subunits of the molecule rotate around the two Co–N single bonds with the result that the two metallabicycles are completely staggered with respect to each other.