Synthesis and structural characterization of ruthenium(II) complexes bearing phosphine-pyrazolyl based tripod ligands

Phosphine-pyrazolyl based tripod ligands ROCH2C(CH2Pz)2(CH2PPh2) (R = H, Me, allyl; Pz = pyrazol-1-yl) were efficiently synthesized and characterized. Reactions of these ligands with [Ru(η6-p-cymene)Cl2]2 afforded complexes of the type [Ru(η6-p-cymene)Cl2](L) (6–8) in which the ligands exhibit κ1-P-coordination to the metal center. Complex [Ru(η6-p-cymene)Cl2{Ph2PCH2C(CH2OH)(CH2Pz)2}] (6) underwent chloride-dissociation in CH2Cl2/MeCN to give complex [RuCl(η6-p-cymene){κ2(P,N)-Ph2PCH2C(CH2OH)(CH2Pz)2}][Cl] (9). Complexes 6–9 demonstrated poor to moderate catalytic activity in the transfer hydrogenation of acetophenone. All these complexes were fully characterized by analytical and spectroscopic methods and their molecular structures were determined by X-ray crystallographic study.