Synthesis, molecular structure and electrochemical investigation of the 1,2,5-thiadiazole-3,4-dithiolate-substituted complex Cp *Ru(NO)(tdas). Evidence for nitrosyl bending during reduction

Abstract

Treatment of disodium 1,2,5-thiadiazole-3,4-dithiol (Na 2tdas) with the cyclopentadienyl complex Cp*Ru(NO)Cl 2 in MeOH gives the corresponding 1,2,5-thiadiazole-3,4-dithiolate-substituted complex Cp *Ru(NO)(tdas) in 61% yield. The product has been characterized in solution by IR and NMR ( 1H and 13C) spectroscopies, and the molecular structure of Cp *Ru(NO)(tdas) has been established by X-ray diffraction analysis. Cp *Ru(NO)(tdas) crystallizes in the monoclinic space group P2 1/ c with a=26.204(2), b=8.4915(6), c=14.2339(9) Å, β=90.739(5)°, V=3166.9(3) Å 3 and Z=8. Full-matrix least-squares refinement yielded R=0.0338 for 3151 ( I>3σ( I)) reflections. The redox properties of Cp *Ru(NO)(tdas) were examined by cyclic and rotating disk electrode voltammetric techniques. Two electrochemical responses were observed and assigned to 0/+1 and 0/ − 1 redox couples. Both of these redox couples are quasi-reversible. It is suggested that the stability of the 0/−1 redox couple is modulated by an EC scheme, whereby the initial reduction product [Cp *Ru(NO)(tdas)] ·− undergoes a bending of the nitrosyl ligand. The nitrosyl bending is observable at low temperature in THF solvent. The nature of the HOMO and LUMO levels in Cp *Ru(NO)(tdas) has been determined by extended Hückel molecular orbital calculations, the results of which are discussed with respect to the electrochemical data.