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

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 ΔG 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 (ΔG = −22 kJ mol −1 ) and CH 3 COCH(O – )CO 2 CH 3  → CH 3 COCH(O – )OCH 3  + CO (ΔG = +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 (ΔG = +9 kJ mol −1 ). The hydride ion transfer in the first step is a key feature of the reaction sequence. Copyright © 2010 John Wiley & Sons, Ltd.