An ‘Old Hydride’ in a new synthesis: a convenient approach to Grubbs-type carbene complexes (PPh3)2Cl2RuCHCHCR2 and their hexacoordinate acetonitrile adducts

A convenient synthetic route to Grubbs-type complexes (PPh3)2Cl2RuCHCHCR2 by reacting Wilkinsonʹs hydride (PPh3)3Ru(H)Cl with propargyl or allenyl chlorides, and the isolation of an adduct complex (CH3CN)(PPh3)2Cl2RuCHCHCMe2 (3) by treatment of (PPh3)3Ru(H)Cl with 3-chloro-3-methyl-1-butyne in the presence of CH3CN are reported. NMR studies in CD2Cl2 show hexacoordinate (CH3CN)(PPh3)2Cl2RuCHCHCMe2 (3) to be in equilibrium with CH3CN and pentacoordinate (PPh3)2Cl2RuCHCHCMe2 (2), the solid state structure of which is presented. X-ray characterization of [(CH3CN)3(PPh3)2RuCHCHCMe2](OTf)2 (6), the first mononuclear, dicationic complex derived from a Grubbs-type carbene, obtained by treatment of (CH3CN)(PPh3)2Cl2RuCHCHCMe2 (3) with trimethylsilyl triflate in the presence of an excess of CH3CN has been performed. This result indicates the possibility of stabilizing such species by labile donor ligands.