文摘
A series of half-sandwich complexes of iridium, rhodium, and ruthenium are shown to be active catalysts for the conversion of aldehydes and water to carboxylic acids. Depending on the catalyst, H2 is either released (the 鈥渁ldehyde鈥搘ater shift鈥? or transferred to a second equivalent of aldehyde (aldehyde disproportionation). Mechanistic studies suggest hydride transfer to be the selectivity-determining step along the reaction pathway. Using [(p-cymene)Ru(bpy)OH2][OTf]2 as precatalyst, we demonstrate a novel example of a highly selective aldehyde鈥搘ater shift in the absence of a hydrogen acceptor or base.
Keywords:
aldehyde oxidation; homogeneous catalysis; dehydrogenation; disproportionation; water