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.