We have previously reported (Tpy)Ru(Pyo)2(OH2) (1  ) (where Tpy=2,2':6',2'-terpyridine and Pyo=2-pyridonate) as a ketone transfer hydrogenation catalyst that acts through an inner-sphere mechanism. ESI-MS of reaction solutions has shown that the catalytic activity is directly correlated to the formation of loosely bridged mixed-valent RuIIRuIII dimers suggesting that electronic coupling within the dimer is key to the reactivity. In an effort to prepare stable dimeric analogs of complex 1  , the complexes (Tpy)Ru(TpyTpy)Ru(Pyo)2(OH2)2+ (2  ), (Tpy)Ru(TpyPhTpy)Ru(Pyo)2(OH2)2+ (3  ), and (Bpy)(Cl)Ru(TpyPhTpy)Ru(Pyo)2(OH2)+ (4  ) where TpyTpy=4',4��-bis(2,2':6',2'-terpyridine) and TpyPhTpy=4,4��-(1,4-phenylene)bis(2,2':6',2�-terpyridine) were prepared by stepwise reaction of (Tpy)Ru(DMSO)Cl2 or (Bpy)Ru(DMSO)2Cl2 and then Ru(DMSO)4Cl2 with the bis(terpyridine) ligand followed by incorporation of the Pyo ligands. Complexes 2  , 3  , and 4  are effective transfer hydrogenation catalysts in 2-propanol and appear to validate the dimer design strategy. Details of ligand and complex synthesis, catalytic evaluation, and early mechanistic investigation will be presented.

Asymmetric bis(terpyridine) ruthenium dimers as ketone transfer hydrogenation catalysts

248th National Meeting (2014)

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