Correspondence of RuIIIRuII and RuIVRuIII Mixed Valent States in a Small Dinuclear Complex

, , , , , , , , , und . Chemistry - A European Journal 18 (18): 5667-5675, S5667/1-S5667/21 (2012)


The diruthenium(III) compd. (m-oxa)Ru(acac)22 1, oxa2- = oxamidato(2-), acac- = 2,4-pentanedionato exhibits an S = 1 ground state with antiferromagnetic spin-spin coupling (J = -40 cm-1). The mol. structure in the crystal of 1·2C7H8 revealed an intramol. metal-metal distance of 5.433 \AA and a notable asymmetry within the bridging ligand. Cyclic voltammetry and spectroelectrochem. (EPR, UV/visible/NIR) of the two-step redn. and of the two-step oxidn. (irreversible 2nd step) produced monocation and monoanion intermediates (Kc = 105.9) with broad NIR absorption bands (e $\sim$2000 -1 cm-1) and maxima at 1800 (1-) and 1500 nm (1+). TD-DFT calcns. support a RuIIIRuII formulation for 1- with a doublet ground state. The 1+ ion (RuIVRuIII) was calcd. with an S = 3/2 ground state and the doublet state higher in energy (DE = 694.6 cm-1). The Mulliken spin d. calcns. showed little participation of the ligand bridge in the spin accommodation for all paramagnetic species (m-oxa)Ru(acac)22n, n = +1, 0, -1, and, accordingly, the NIR absorptions were identified as metal-to-metal (intervalence) charge transfers. Whereas only one such NIR band was obsd. for the RuIIIRuII (4d5/4d6) system 1-, the RuIVRuIII (4d4/4d5) form 1+ exhibited extended absorbance over the UV/visible/NIR range. on SciFinder(R)

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