Ruthenium(II) hydride complexes of 2,6-(diphenylphosphinomethyl)pyridine

A series of PNP-ruthenium(II) complexes Ru(OCOMe)(2)(PNP) (1), Ru(OCOMe)(2)(PNP)(PPh3) (2), the monohydrides RuHX(PNP)(PPh3) (X = OCOMe (3); X = Cl (4)), and dihydride RuH2(PNP)(PPh3) (5) (PNP = 2,6-bis(diphenylphosphinomethyl)pyridine) were synthesized and characterized by microanalysis as well as NMR, IR, and mass spectroscopies. The solution dynamics of complex 1 were studied by variable-temperature H-1 and P-31{H-1} NMR spectroscopies. The crystal structure of RuHCl(PNP)(PPh3) (4) was determined by X-ray crystallography, showing that the PNP ligand coordinates the Ru atom in a meridional mode. The hydride complexes RuH(OCOMe)(PNP)(PPh3) (3) and RuH2(PNP)(PPh3) (5) undergo deuterium exchange reactions with CD3OD to give substitution of both the hydrides and PNP methylene protons by deuterium. The probable intermediates involved in these exchange processes are molecular dihydrogen complexes of Ru(II).