Are the anions MeO(CO)n- (n=1 and 2) methoxide anion donors in the gas phase? A theoretical investigation

Abstract

1. The anions CH(3)O-(-)CO and CH(3)OCO-(-)CO are both methoxide anion donors. The processes CH(3)O-(-)CO --> CH(3)O(-) + CO and CH(3)OCO-CO --> CH(3)O(-) + 2CO have DeltaG values of +8 and -68 kJ mol(-1), respectively, at the CCSD(T)/6-311++G(2d, 2p)//B3LYP/6-311++G(2d,2p) level of theory. 2. The reactions CH(3)OCOCO(2) (-) --> CH(3)OCO(2) (-) + CO (DeltaG = -22 kJ mol(-1)) and CH(3)COCH(O(-))CO(2)CH(3) --> CH(3)COCH(O(-))OCH(3) + CO (DeltaG = +19 kJ mol(-1)) proceed directly from the precursor anions via the transition states (CH(3)OCO...CO(2))(-) and (CH(3)COCHO...CH(3)OCO)(-), respectively. 3. Anion CH(3)COCH(O(-))CO(2)CH(3) undergoes methoxide anion transfer and loss of two molecules of CO in the reaction sequence CH(3)COCH(O(-))CO(2)CH(3) --> CH(3)CH(O(-))COCO(2)CH(3) --> [CH(3)CHO (CH(3)OCO-(-)CO)] --> CH(3)CH(O(-))OCH(3) + 2CO (DeltaG = +9 kJ mol(-1)). The hydride ion transfer in the first step is a key feature of the reaction sequence.