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

摘要

Crystal structures of a kind of cyclohexyl-cobaldioxime coenzyme B-12 model compounds RCo(chgH)(2)L (R = CH3, C2H5 or C3H7, L = pyridine or H2O, chgH = 1,2-cyclohexanedione dioxime) at room and low temperatures have been determined. The results for C2H5Co(chgH)(2)py (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 CH3Co(chgH)(2)py (2), C2H5Co(chgH)(2)H2O (3), and C3H7Co(ch-H)(2)H2O (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. (c) 2005 Elsevier B.V. All rights reserved.