Ruthenium complexes supported by 2,6-bis(pyrazol-1-yl)pyridines

The synthesis and characterization of a series of ruthenium(II) complexes containing the planar tridentate ligands 2,6-bis(pyrazol-1-yl)pyridine (BPP) or 2,6-bis(3,5-dimethylpyrazol-1-yl)pyridine (Me4BPP) are described. The reaction of BPP with RuCl2(PPh3)(3) yields both the cis (1a) and trans (1b) isomers of [RuCl(PPh3)(2)(BPP)]Cl. Complexes of the general formula transRuCl(2)(L)(Me4BPP) (L=PPh3, 2; C2H4, 3a; CO, 3b; MeCN, 3c) are also reported, and were prepared from either RuCl2(PPh3)(3) and Me4BPP (i.e. 2), Et3N reductions of RuCl3(Me4BPP) in the presence of L (i.e. 2 and 3b,c), or from [RuCl2(p-cymene)](2), Me4BPP and L (i.e. 3a). The neutral vinylidene complex cis-RuCl=(=C=CHPh)(Me4BPP) (4), was isolated from reactions of phenylacetylene with either 3a or mixtures of [RuCl2(p-cymene)](2) and Me4BPP, while the cationic allenylidene complex [RuCl(PPh3)(=C=C=CPh2)(Me4BPP)][BF4] (5), was prepared from 2, AgBF4 and 1,1-diphenyl-2-propyn-1-ol. Complexes 1-5 were characterized by multinuclear NMR and IR spectroscopy. (C) 2002 Elsevier Science B.V. All rights reserved.