SYNTHESIS OF THE PENTAMETHYLCYCLOPENTADIENYLRUTHENIUM DITHIOLATE COMPLEX CP-ASTERISK-RU(NO)(DMIT) - ELECTROCHEMICAL PROPERTIES AND EXTENDEDHUCKEL MOLECULAR-ORBITAL CALCULATIONS

The new compound CpRu(NO)(dmit) has been prepared from Cp*Ru(NO)Cl-2 and 1,3-dithiol-2-thione-4,5-dithiolate (dmit), prepared in situ from 4,5-bis(benzoylthio)-1,3-dithiol-2-thione in ethanolic sodium ethoxide , in moderate yield. The product has been isolated and characterized i n solution by IR and NMR (H-1 and C-13) spectroscopies. The solid-stat e structure of CpRu(NO)(dmit) has been confirmed by single-crystal X- ray diffraction analysis. The electrochemical behavior of CpRu(NO)(dm it) has been studied by cyclic and rotating disk electrode voltammetri es, revealing the existence of two well-defined one-electron responses that have been assigned to the 0/+1 and 0/-1 redox couples. The compo sition of the HOMO and LUMO levels in the model compound CpRu(NO)(dmit ) has been determined by carrying out extended Huckel molecular orbita l calculations. The MO data indicate that the HOMO in CpRu(NO)(dmit) i s best described as a dmit-based orbital (78%) which contains a small amount of Ru (d(x2-y2))/NO(py) character, while the LUMO is best repre sented by an antibonding overlap of the Ru (d(xy)) and pi NO (p(x)) o rbitals. A comparison of the MO and electrochemical data from CpRu(NO )(dmit) with the structurally related dithiolate compounds CpRu(NO)(m nt) and CpRu(NO)(tdas) is presented. It has been found that Cp*Ru(NO) (dmit) exhibits a more easily oxidized 0/+1 redox couple as compared t o the mnt and tdas compounds. This results from the presence of a high -lying [dmit](2-) donor orbital that leads to a high-energy antibondin g interaction between the CpRu(NO) and dmit fragments, which in turn produces a destabilized HOMO.