Synthetic, X-ray diffraction, electrochemical, and density functional theoretical studies of (indenyl)ruthenium complexes containing dithiolate ligands

Abstract

Halide substitution of the complexes [(Ind)Ru(L2)X] {Ind = η5-C9H7. 1: (L2) = dppf [1,1′-bis(diphenylphosphanyl)ferrocene], X = Cl; 2: (L2) = dppm [1,1′-bis(diphenylphosphanyl)methane], X = Cl; and 18: (L2) = (CO)2, X = I} with the 1,1-dithiolates -S 2CNR2 (dialkyl dithiocarbamates for R = Me, Et, and C 5H10), S2COR (alkyl xanthates for R = Et and iPr), and -S2PR2 (dithiophosphinates for R = Et and Ph) showed that the lability of the indenyl ligand is influenced by the nature of both the coligand and the incoming dithiolate, as well as the solvent. In addition to dithiolate derivatives, the reactions also produced the hydride species [(Ind)Ru(diphos)H] in solvent- and stoichiometry-dependent yields. The observed dependence of lability of Ind on (L2) follows the order, dppf < dppm ≈ (CO)2, in agreement with the electron-donor capability of L2, as well as the estimation of lowest activation energy for the η5 → η3 ring slippage process in the series of complexes [(Ind)Ru(L)2(S2COMe)] (L = PMeH2, PH3, CO) for L = CO. The computational study also indicated an indenyl lability order for dithiolate substitution (dithiocarbamate > xanthate), in agreement with experimental findings. The dissociation of the indenyl ligand in chloro substitution of 1 by -S 2CNEt2 was found to be exhaustive in a polar solvent like MeOH, but only partial in CH2Cl2. Cyclic voltammetry experiments indicated that [(Ind)Ru(dppf)(η1-S2COiPr)] (10) and [(Ind)Ru(dppf)(η1-S2PPh2)] (13) can be oxidized in one-electron chemical irreversible or chemical reversible processes, respectively (at a scan rate of 100 mV/s), at about 0 V versus Fc/Fc+. Complex 13 underwent additional one-electron oxidation processes at +0.5 and +0.8 V versus Fc/Fc+. The new complexes have all been characterized spectroscopically, and some (four containing the indenyl ligand and three of the non-indenyl type) by X-ray diffraction as well. © Wiley-VCH Verlag GmbH & Co. KGaA, 2007.