New piano-stool ruthenium(II) complexes of benzene and bidentate/tridentate nitrogen-donor ligands: synthesis and characterization

New piano-stool ruthenium(II) complexes, [Ru(η6-C6H6)L1]2+, [Ru(η6-C6H6)(L2)Cl]+, [Ru(η6-C6H6)(L3)Cl]+, [Ru(η-C6H6)(L4)Cl]+ and [Ru(η6-C6H6)(L5)Cl]+ have been isolated as their hexafluorophosphate salts by bridge-cleavage reactions of [{Ru(η6-C6H6)Cl2}2] in methanol with the potentially tri- and bi-dentate nitrogen-containing ligands [2-(2-pyridyl)ethyl](2-pyridylmethyl)methylamine (L1), 2,6-bis(pyrazol-1-ylmethyl)pyridine (L2) and its tetramethyl-substituted derivative (L3), 2-(pyrazol-1-ylmethyl)pyridine (L4) and its dimethyl derivative (L5). The structures of these compounds in MeCN solution have been elucidated by 1H NMR spectroscopy. The complex [Ru(η6-C6H6)L1][PF6]2 has been characterized by single-crystal X-ray crystallography: triclinic, space group P(no. 2), a= 7.790(3), b= 10.039(3). c= 16.679(5)Å, α= 88.31 (2), β= 83.15(3), γ= 77.1 9(3)° and Z= 2. The structure has been refined to an R factor of 0.063 based on 5330 observed reflections. Average Ru–C and Ru–N (two types) bond lengths are 2.202(6) and 2.114(5) and 2.170(5)Å respectively.