| Abstract: | The ligand (6,6′-dimethoxybiphenyl-2,2′-diyl)bis3,5-di(tert-butyl)phenylphosphine] ( 1 ) forms an unexpectedly stable hydrido-bis-solvento complex of composition RuH(isopropanol)2( 1 )]BF4, ( 2 ) under the conditions used in the enantioselective hydrogenation of pyrones. The structure of 2 , determined by X-ray diffraction, represents the first well-characterized chiral five-coordinate bis-phosphine ruthenium-hydride complex stable as a solvento complex, and provides a structural link in the enantioselective pyrone hydrogenation cycle catalyzed by Ru(OAc)2( 1 )]. Using the arene complex RuH(p-cymene)( 1 )]BF4 ( 3 ), the chiral pocket of coordinated 1 is shown to be relatively rigid, via NMR spectroscopy. This is reflected in restricted rotation about one of the four P–3,5-di(tert-butyl)phenyl] P? Cipso bonds at room temperature. |
