[Ru(PPh < inf > 3 < /inf > ) < inf > 3 < /inf > Cl < inf > 2 < /inf > ]-mediated transformation of -CH < inf > 3 < /inf > into =CHPHPh < inf > 3 < /inf > in biacetylmonoxime acetyl-/aroylhydrazones: Ruthenium(III) complexes with the transformed ligands

Abstract

Ruthenium(III) complexes of general formula trans-[Ru(tL)- (PPh3)Cl2] have been isolated in 58-73% yields from reactions between [Ru(PPh3)3Cl2] and tridentate Schiff bases (H2L) derived from biacetylmonoxime and acid hydrazides in methanol. The X-ray structures of the complexes reveal unprecedented conversions of methyl groups in the biacetyl fragments of the Schiff bases into triphenyl-vinyl-λ5-phosphane (=CHPHPh3) moieties in the transformed ligands (tL-). The metal centre in each complex is in a distorted octahedral N2OPCl2 coordination sphere made up of the meridionally spanning N,N,O-donor tL -, PPh3 and two mutually trans-oriented chlorides. In their electronic spectra, the complexes each display four absorptions due to ligand-to-metal and ligand-centred transitions in the 463-260 nm range. All the complexes are one-electron paramagnetic (μeff. at 298 K = 1.81-2.06 μB) and display rhombic EPR spectra in frozen (120 K) dichloromethane/toluene (1:1) solutions. Cyclic voltammograms of the complexes in dimethylformamide solutions show substituent-sensitive, quasi-reversible RuIV/RuIII and RuIII/RuII couples in the potential ranges of 0.46 to 0.54 V and -0.53 to -0.42 V (vs. Ag/AgCl), respectively. © Wiley-VCH Verlag GmbH & Co. KGaA, 2009.