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EPR and 1H NMR spectroscopy and DFT study of pentaammineruthenium(III)phenylcyanamide complexes

, , , , and . Inorganica Chimica Acta, 374 (1): 147--151 (2011)
DOI: 10.1016/j.ica.2011.01.105

Abstract

The EPR and 1H NMR spectroscopy of seven Ru(NH3)5L2+ complexes, where L = 3,5-dimethoxyphenylcyanamide (MeO2pcyd), 3,4,5-trimethoxyphenylcyanamide (MeO3pcyd), 4-nitrophenylcyanamide (NO2pcyd), 2,3-dichlorophenylcyanamide (Cl2pcyd), 2,4,6-trichlorophenylcyanamide (Cl3pcyd), 2,3,5,6-tetrachlorophenylcyanamide (Cl4pcyd) and pentachlorophenylcyanamide (Cl5pcyd), was performed. EPR spectra of the complexes showed an axial signal with g|| and g$\bot$ at high and low field, resp. The g || axis is suggested to lie along the Ru-cyanamide bond. Gas-phase DFT calcns. of Ru(NH3)5 phenylcyanamide2+ showed spin d. localized mostly on the phenylcyanamide ligand, in disagreement with EPR data. DFT/polarizable continuum model (PCM, water solvation) calcns. shifted spin d. towards ruthenium so that spin d. was shared between ruthenium and phenylcyanamide ligand. Proton contact shifts were detd. from NMR and EPR data and were used to est. spin d. distributions on Ph ring carbons. The results showed that the DFT/PCM calcn. overestimated spin d. on Ph ring carbons by approx. one order of magnitude. Donor-acceptor interactions between the solute and solvent that are not fully accounted for in the DFT/PCM method are suggested to stabilize the Ru(III) oxidn. state. on SciFinder(R)

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