Influence of Hydrogen Bonding on the Spectroscopic Properties and on the Reactivity of Ruthenium Hydrido Dihydrogen Complexes

The reaction of RuH 2 (H 2 ) 2 (PCy 3 ) 2 ( 1 ) with L−X in pentane at room temperature yields new hydrido derivatives of ruthenium accommodating a stretched H−H bond, namely RuH(H 2 )(L−X)(PCy 3 ) 2 (L−X = C 5 H 4 N−O, 2; L−X = C 5 H 4 N−NH, 3 ). NMR studies show that hydrogen bond donors (substituted phenols, hexafluoro-2-propanol, etc.) interact with the hydrides in the case of 2, whereas for 3 an equilibrium with the cation [RuH(H 2 )(py-NH 2 )(PCy 3 ) 2 ] + is attained. The latter species has been isolated in the form of the [B(C 6 F 5 ) 4 ] salt, 4, independently prepared by addition of (PhNMe 2 H)[B(C 6 F 5 ) 4 ] to 3 . These phenomena explain the difference of reactivity with olefins between 2 and 3 in nonpolar media or in the presence of alcohols.