Syntheses, Structures, and Properties of Mono- and Dinuclear Acetylacetonato Ruthenium(III) Complexes with Chlorido or Thiocyanato Ligands

Abstract

The mononuclear and dinuclear ruthenium(III) complexes trans-Ph4P[RuIII(acac)2Cl2] (1), Ph4P[{RuIII(acac)Cl}2(μ-Cl)3] (2) and trans-Ph4P[RuIII(acac)2(NCS)2]·0.5C6H14 (3·0.5C6H14) were synthesized. Single crystals of 1, 2·H2O and 3·CH3CN suitable for X-ray crystal structure analyses were obtained through recrystallization from DMF for 1 and 2·H2O and from acetonitrile for 3·CH3CN. An octahedral Ru with bis-chelate-acac ligands and axial chlorido or κ-N-thiocyanido ligands (for 1 and 3·CH3CN) and triply µ-chlorido-bridged dinuclear Ru2 for 2·H2O were confirmed through the structure analyses. The Ru–Ru distance of 2.6661(2) of 2·H2O is indicative of the existence of the direct metal–metal interaction. The room temperature magnetic moments (μeff) are 2.00 and 1.93 μB for 1 and 3·0.5C6H14, respectively, and 0.66 μB for 2. The temperature-dependent (2–300 K) magnetic susceptibility showed that the strong antiferromagnetic interaction (J ≤ −800 cm−1) is operative between the ruthenium(III) ions within the dinuclear core. In the 1H NMR spectra measured in CDCl3 at 298 K, the dinuclear complex 2 showed signals for the acac ligand protons at 2.50 and 2.39 ppm (for CH3) and 5.93 ppm (for CH), respectively, while 1 and 3·0.5C6H14 showed signals with large paramagnetic shifts; −17.59 ppm (for CH3) and −57.01 ppm (for CH) for 1 and −16.89 and −17.36 ppm (for CH3) and −53.67 and −55.53 ppm (for CH) for 3·0.5C6H14. Cyclic voltammograms in CH2Cl2 with an electrolyte of nBu4N(ClO4) showed the RuIII → RuIV redox wave at 0.23 V (vs. Fc/Fc+) for 1 and the RuIII → RuII waves at −1.39 V for 1 and −1.25 V for 3·0.5C6H14 and the RuIII–RuIII → RuIII–RuIV and RuIII–RuIII → RuIII–RuIV waves at 0.91 V and −0.79 V for 2.