The Ru(III) complexes, [(NH3)5Ru(LH)]2+, where LH = Me2dicydH-, dicydH-, and Cl2dicydH-, and the deprotonated complexes [(NH3)5Ru(L)]+, have been prepared and characterized by electronic absorption spectroscopy and cyclic voltammetry. The Ru(IV) complex, [(NH3)5Ru(Me2dicyd)]2+, was also synthesized and a qualitative spectroscopic analysis permitted comparison of the LMCT transitions of the Ru(III)-cyanamide and Ru(IV)-cyanamide chromophores. [(NH3)5Ru(Me2dicyd)]2+ is diamagnetic and its 1H NMR spectrum showed significant anisotropy in chemical shifts between trans and cis ammine proton resonances. It was suggested that preferential hyperconjugation of the ammine N-H bonds with the b1* (π antibonding) orbital of the Ru(IV)-cyanamide chromophore withdrew electron density from the N-H bonds and deshielded the hydrogen nuclei. This hyperconjugation mechanism was also invoked to explain the dramatic anisotropy in contact shifts of trans and cis ammines in the 1H NMR spectrum of the [Ru(IV), Ru(III)] mixed valence complex [{(NH3)5Ru}2(μ-Me2dicyd)] 5+.

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Inorganica Chimica Acta
Ottawa-Carleton Chemistry Institute

Naklicki, M.L. (Mark L.), White, C.A. (Christopher A.), Kondratiev, V.V. (Veniamin V.), & Crutchley, R. (1996). Mononuclear and dinuclear ruthenium(III) and ruthenium(IV) complexes of 1,4-dicyanamido-2,5-dimethylbenzene dianion. Inorganica Chimica Acta, 242(1-2), 63–69.