Reactivity studies of (η6-arene)ruthenium dimeric complexes towards pyrazoles: isolation of amidines, bis pyrazoles and chloro bridged pyrazole complexes

The complex [(η6-p-cymene)Ru(μ-Cl)Cl]21 reacts with pyrazole ligands (3a–g) in acetonitrile to afford the amidine derivatives of the type [(η6-p-cymene)Ru(L)(3,5-HRR′pz)](BF4)2 (4a–f), where L = {HNdouble bond; length as m-dashC(Me)3,5-RR′pz}; R, R′ = H (4a); H, CH3 (4b); C6H5 (4c); CH3, C6H5 (4d) OCH3 (4e); and OC2H5 (4f), respectively. The ligand L is generated in situ through the condensation of 3,5-HRR′pz with acetonitrile under the influence of [(η6-p-cymene)RuCl2]2. The complex [(η6-C6Me6)Ru(μ-Cl)Cl]22 reacts with pyrazole ligands in acetonitrile to yield bis-pyrazole derivatives such as [(η6-C6Me6)Ru (3,5-HRR′pz)2Cl](BF4) (5a–b), where R, R′ = H (5a); H, CH3 (5b), as well as dimeric complexes of pyrazole substituted chloro bridged derivatives [{(η6-C6Me6)Ru(μ-Cl) (3,5-HRR′pz)}2](BF4)2 (5c–g), where R, R′ = CH3 (5c); C6H5 (5d); CH3, C6H5 (5e); OCH3 (5f); and OC2H5 (5g), respectively. These complexes were characterized by FT-IR and FT-NMR spectroscopy as well as analytical data. The molecular structures 1 of representative complexes [(η6-C6Me6)Ru{3(5)-Hmpz}2Cl]+5b, [(η6-C6Me6)Ru(μ-Cl)(3,5-Hdmpz)]22+5c and [(η6-C6Me6)Ru(μ-Cl){3(5)Me,5(3)Ph-Hpz}]22+5e were established by single crystal X-ray diffraction studies.