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

Abstract

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 P1^-(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.