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 [RuCl2(PPh3)3] and one or two equivalent amounts of 1-[(P-diphenyl)-2-phosphinoethyl]-3,5-dimethylpyrazole (1) in dichloromethane gave [RuCl2(PPh3)(1)] (2) or [RuCl2(1)2] (3), respectively, in good yields. Activation of propargylic alcohol derivatives by 3 in refluxing dichloromethane and in the presence of NaBPh4 lead to the new allenylidene ruthenium complexes [RuCl(1)2(CCCPhCH3)][BPh4] ([4][BPh4]) and [RuCl(1)2(CCCPh2)][BPh4] ([5][BPh4]). The reaction between 3 and phenylacetylene in dichloromethane and in the presence of KPF6 affords the vinylidene complex [RuCl(1)2(CCHPh)][PF6] ([6][PF6]). The X-ray diffraction studies of 2, 3, and [5][BPh4] are reported.