Synthesis, NMR studies, and molecular orbital calculations on cyclohexadienyl derivatives of (η6-arene)tris(pyrazolyl)ruthenium(II) compounds

Abstract

The addition of nucleophiles to the complex cations [Ru(η⁶-arene){κ³-HB(Pz₃)}]⁺ or [Ru(η⁶-arene){κ³-HC(Pz₃)}]²⁺ (Pz = pyrazol-1-yl) proceeds smoothly to give [Ru(η⁵-cyclohexadienyl){κ³-HB(Pz₃)}] or [Ru(η⁵-cyclohexadienyl){κ³-HC(Pz₃)}]⁺ respectively, which have been identified by NMR spectroscopy. NMR spectroscopy reveals that each of the cyclohexadienyl derivatives exhibits significant barriers to rotation of the η⁵ ligand. The electronic structure of [Ru(η⁶-arene){κ³-HB(Pz₃)}]⁺ and the cyclohexadienyl derivatives has been probed by extended Hückel molecular orbital calculations, with emphasis on the rationalisation of the experimentally observed barriers to rotation of the carbocycles. The single crystal structure of [Ru(η⁵-C₆H₆CN){κ³-HC(Pz₃)}][PF₆] is reported.