Synthesis, structure and redox properties of isomeric [RuCl2(L)2] (L = N-aryl-1,2-arylenediimine) complexes formed by the oxidative dimerization of coordinated aromatic amines
Journal
Polyhedron
Journal Volume
21
Journal Issue
1
Pages
97-104
Date Issued
2002
Author(s)
Abstract
The di-arylamino complex [RuCl2(ArNH2)2L] (ArNH2 = aromatic monoamine and L = N-aryl-1,2-diimino arene) reacts spontaneously with aqueous H2O2 to produce two isomers of [RuCl2(L)2] via oxidative dimerization of the two coordinated aromatic amines. The geometries of two isomers are cis with respect to two chlorides and are trans, cis(tc) and cis, cis(cc) in the following sequence: NH(imine), HN(imine) and ArN(imine), ArN(imine). Of the above two, the tc-[RuCl2(L)2] forms good X-ray quality crystals. The structure of a representative has been solved by X-ray diffraction. The geometry of the cc-[RuCl2(L)2] is, however, revealed by the spectral data. The tc-isomer possesses a C2-symmetry axis and the two-coordinated diimine ligands are magnetically equivalent. As a result, a single NH resonance in tc-[RuCl2(L)2] appeared at approximately δ 12.40. By contrast, the cc-isomer is unsymmetrical and a complex pattern of 1H NMR was observed in this case. Thus, there were two NH resonances observed in the range approximately δ 14.11-11.88. A semi-empirical extended Hückel MO calculations on a representative example showed strong metal-ligand overlap. A highly intense electronic transition that appeared in the visible range spectra of the complexes was assigned to a transition involving two molecular orbitals with considerable metal and ligand contributions. Both the isomers of the complex showed a high potential anodic response (0.8 V) due to the RuIII/RuII couple. The trivalent congeners [RuCl2(L)2]+ were generated in solution which showed characteristic rhombic EPR for the low spin d5 ions. The distortion parameters have been computed using the observed g values. The axial distortion (Δ) in each case is found to be stronger than the rhombic (V) distortion. © 2002 Elsevier Science Ltd. All rights reserved.
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Type
journal article