Structure and thermal decomposition studies on alkylcobaloxime B 12 model compounds with 1,2-cyclohexanedione dioxime as equatorial ligand

Abstract

Crystal structures of a kind of cyclohexyl-cobaldioxime coenzyme B 12 model compounds RCo(chgH) 2L (R = CH 3, C 2H 5 or C 3H 7, L = pyridine or H 2O, chgH = 1,2-cyclohexanedione dioxime) at room and low temperatures have been determined. The results for C 2H 5Co(chgH) 2py ( 1) indicate that its crystal unit parameters vary with temperatures, and two sides of cyclohexyls on the equatorial plane assume disorder accompanying a temperature dependent conformation occupation change. Interestingly, there has been observed a proton shift from one chgH ligand to the other one for 1 when the temperature decreases. Whilst a similar chair-form configuration with disordered chgH is found at 293 K for CH 3Co(chgH) 2py ( 2), C 2H 5Co(chgH) 2H 2O ( 3), and C 3H 7Co(chgH) 2H 2O ( 4), respectively. In addition, molecular and crystal packing structures, as well as thermal decomposition properties of the four complexes are investigated and compared with other cobaloxime models.