[RuCp(PR3)(CH3CN)2]PF6 (R = Ph, Me, Cy).: Convenient precursors for mixed ruthenium(II) and ruthenium(IV) half-sandwich complexes

The reaction of [RuCp(CH3CN)(3)]PF6 (1) with the monodentate ligands PR3 (R = Me, Ph, Cy) affords the cationic complexes [RuCp(PR3)(CH3CN)(2)]PF6 (2a-c) in high yields. The CH3CN exchange kinetics has been studied by NMR, suggesting a dissociative mechanism. Due to van der Waals repulsive interactions between PCy3 and the nitrile ligands, CH3CN is particularly labile in 2c. The chemistry of 2a-c has been further investigated with respect to substitution and oxidative addition.