Synthesis of Ru(II) complexes of the new 1-[(P-diphenyl)-2-phosphinoethyl]-3,5-dimethylpyrazole ligand and study of their reactivity toward terminal alkynes

The reaction between [RuCl 2 (PPh 3 ) 3 ] and one or two equivalent amounts of 1-[(P-diphenyl)-2-phosphinoethyl]-3,5-dimethylpyrazole (1) in dichloromethane gave [RuCl 2 (PPh 3 )(1)] (2) or [RuCl 2 (1) 2 ] (3), respectively, in good yields. Activation of propargylic alcohol derivatives by 3 in refluxing dichloromethane and in the presence of NaBPh 4 lead to the new allenylidene ruthenium complexes [RuCl(1) 2 (C=C=CPhCH 3 )][BPh 4 ] ([4][BPh 4 ]) and [RuCl(1) 2 (C=C=CPh 2 )][BPh 4 ] ([5][BPh 4 ]). The reaction between 3 and phenylacetylene in dichloromethane and in the presence of KPF 6 affords the vinylidene complex [RuCl(1) 2 (C=CHPh)][PF 6 ] ([6][PF 6 ]). The X-ray diffraction studies of 2, 3, and [5][BPh 4 ] are reported. © 2002 Elsevier Science B.V. All rights reserved.