Synthesis, Characterization, and Variable-Temperature 1H NMR Behavior of Organo-Bridged Dicobaloximes
摘要:
Organo-bridged dicobaloximes with four different dioximes Py(L)(2)CoCH2-R-CH2Co(L)(2)Py (L = dmgH, dpgH, chgH, and gH) have been synthesized and characterized by H-1 and C-13 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 Co-III to Co-I takes place. The Co-C bond in 4a cleaves during crystallization and results in the formation of o-vinylbenzyl cobaloxime. The variable-temperature H-1 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.
Benzylbis(dimethylglyoximato)pyridinecobalt(III) reacts with bromotrichloromethane at from 50 to 90°C in chloroform to give good yields of trichloroethylbenzene, which are higher when imidazole is present in the reaction mixture. Methyl- and polymethyl-substituted benzylbis(dimethylglyximato)pyridinecobalt(III) complexes give higher yields of the corresponding trichloroethylarenes (85–90%), whereas