Terpyridine ruthenium complexes bearing 2-pyridonato ligands have been previously reported to catalyze ketone transfer hydrogenation in alcohol solvents through loosely bound mixed valent RuIIRuIII dimer intermediates. In an effort to prepare structurally stable analogs, 4',4��-bis(2,2':6',2�-terpyridine) and 4',4��-(1,4-phenylene)bis(2,2':6',2�-terpyridine) bridged ruthenium dimers have been prepared with one ruthenium capped with 2,2':6',2'-terpyridine or 2,2'-bipyridine and the other bearing 2-pyridonato ligands. As intended, these complexes catalyze ketone transfer hydrogenation in alcohol solvents. Ligand substitution effects suggest that RuIIRuIII mixed valent intermediates are key to the catalytic cycle and that the RuIII is localized at the active site by the 2-pyridonato ligands. DFT calculations suggest that electronic coupling through the bis(terpyridine) bridge stabilizes the RuIIRuIII oxidation state and supports the active RuIII center.

Asymmetric polypyridine ruthenium dimers as catalysts for ketone transfer hydrogenation

248th National Meeting (2014)

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