Synthesis and Reactivity of Ampy-Based Ruthenium(II) Catalysts forTransfer Hydrogenation of Ketones

Four ruthenium(II) complexes of the motif,cis-RuCl2[Ph2P(CH2)4PPh2](ampy-L) andtrans-RuCl2[Ph2P-(CH2)4PPh2](ampy-L) (ampy = 2-(aminomethyl)pyridine; L =Cl or OMe), were synthesized for potential catalytic applications.The complexes were fully characterized using NMR spectroscopy,UV-vis spectroscopy, X-ray crystallography, and electrochemicalanalyses. Thetrans-isomer was observed to undergo isomerizationto thecis-isomer, and kinetic studies of the isomerization reactionshowed that subtle changes in ampy-L electron density did notimpact the rate oftrans-to-cisisomerization. To probe the utility ofthese complexes toward catalysis, transfer hydrogenation reactionswere performed for the reduction of a variety of ketones. All threecis-complexes showed high rates and yields toward ketone transfer hydrogenation.