Ruthenium Phosphine/Diimine Complexes:  Syntheses, Characterization, Reactivity with Carbon Monoxide, and Catalytic Hydrogenation of Ketones

Abstract

The cis -[RuCl 2 (PPh 3 ) 2 (N−N)] (N−N = bipy ( 1 ), Me-bipy ( 2 ), phen ( 3 ), and bathophen ( 4 )) complexes were used to synthesize five new electron-rich phosphine-containing complexes cis -[RuCl 2 (dcype)(N−N)] (N−N = bipy ( 1a ), Me-bipy ( 2a ), phen ( 3a ), and bathophen ( 4a )) and cis -[RuCl 2 (PEt 3 ) 2 (bipy)] ( 1c ) by phosphine exchange. These complexes were obtained and characterized by NMR ( 31 P{ 1 H}, 1 H), cyclic voltammetry, and elemental analysis. Electrochemical studies of these complexes reveal a single reduction process (Ru III /Ru II ). These complexes are more easily oxidized than their analogues cis -[RuCl 2 (dppb)(N−N)]. The reactivity of complexes cis- [RuCl 2 (dcype)(N−N)] with carbon monoxide was tested, and dissociation of one chloride was observed, leading to the formation of four new cationic species with general formula [RuCl(CO)(dcype)(N−N)](PF 6 ) (bipy ( 1b ), Me-bipy ( 2b ), phen ( 3b ), and bathophen ( 4b )). The complexes described here and elsewhere with general formulas cis- [RuCl 2 (P−P)(N−N)], [RuCl(CO)(dcype)(N−N)](PF 6 ), and cis- [RuCl 2 (P) 2 (N−N)] were used as precatalysts in the transfer hydrogenation of functionalized aryl-ketones, and most of them were active. X-ray structures of cis -[RuCl 2 (PEt 3 ) 2 (bipy)] ( 1c ) and [RuCl(CO)(dcype)(bipy)](PF 6 ) ( 1b ) will be presented.