Nickel-Mediated Stepwise Transformation of CO to Acetaldehyde and Ethanol

The insertion of CO into the Ni-C bond of synthetic Ni(II)-CH3 cationic complex ([1-CH3](+)) affords a nickel-acetyl complex ([1-COCH3](+)). Reduction of resultant [1-COCH3](+) by borohydrides produces CH3CHO, CH3CH2OH, and an Ni(0) compound ([1](0)), which can react with CH3I to regenerate [1-CH3](+). By conducting deuterium labeling experiments, we have demonstrated that CH3CHO is the primary product from CH3CH2OH in such CO transformation reactions. In the reduction of [1-COCH3](+), the formation of CH3CHO competes with the loss of CH4, which leads to a Ni(0)-CO compound ([1-CO](0)) as a minor product. Our results establish fundamental steps in the exploration of nickel-mediated CO transformation to valuable chemicals.