Synthesis, Characterization, and Variable-Temperature 1H NMR Behavior of Organo-Bridged Dicobaloximes

Organo-bridged dicobaloximes with four different dioximes Py(L)2CoCH2-R-CH2Co(L)2Py (L = dmgH, dpgH, chgH, and gH) have been synthesized and characterized by 1H and 13C NMR and FAB mass spectroscopy. The cis influencing order observed in dicobaloximes is similar to the previously observed order in monocobaloximes. The cyclic voltammetric results show that an irreversible single-step two-electron reduction of CoIII to CoI takes place. The Co−C bond in 4a cleaves during crystallization and results in the formation of o-vinylbenzyl cobaloxime. The variable-temperature 1H NMR study suggests that the Co−C bond rotation is restricted and its magnitude depends on both the nature of the bridging ligand and the dioxime.