The diruthenium(III) compound [(μ-oxa){Ru(acac) 2} 2] [1, oxa 2-=oxamidato(2-), acac -=2,4- pentanedionato] exhibits an S=1 ground state with antiferromagnetic spin-spin coupling (J=-40 cm -1). The molecular structure in the crystal of 1â2C 7H 8 revealed an intramolecular metal-metal distance of 5.433 Å and a notable asymmetry within the bridging ligand. Cyclic voltammetry and spectroelectrochemistry (EPR, UV/Vis/NIR) of the two-step reduction and of the two-step oxidation (irreversible second step) produced monocation and monoanion intermediates (K c=10 5.9) with broad NIR absorption bands (Îμ ca. 2000M -1cm -1) and maxima at 1800 (1 -) and 1500 nm (1 +). TD-DFT calculations support a Ru IIIRu II formulation for 1 - with a doublet ground state. The 1 + ion (Ru IVRu III) was calculated with an S=3/2 ground state and the doublet state higher in energy (ÎE=694.6 cm -1). The Mulliken spin density calculations showed little participation of the ligand bridge in the spin accommodation for all paramagnetic species [(μ-oxa){Ru(acac) 2} 2] n, 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 observed for the Ru IIIRu II (4d 5/4d 6) system 1 -, the Ru IVRu III (4d 4/4d 5) form 1 + exhibited extended absorbance over the UV/Vis/NIR range. © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.