Activation of molecular oxygen by a dioxygenase pathway by a ruthenium bis-bipyridine compound with a proximal selenium site.

A ruthenium(II) bipyridine complex with proximal phenylselenium tethers, Ru(2), reacted intramolecularly with O(2) in a protic slightly acidic solvent, 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP), to yield an O-O bond cleaved product, Ru(2), with formation of two Ru-O-Se moieties. This stable compound was isolated, and its structure was determined by X-ray diffraction. The identification of the compound in solution was confirmed by ESI-MS and the (1)H NMR with the associated Curie plot that showed that Ru(2) was paramagnetic. The magnetic susceptibility was 2.8 mu(B) by Evan's method suggesting a ground state triplet or biradical. DFT calculations, however, predicted a ground state singlet and an oxidized Se atom. Further it was shown that Ru(2) is a potent oxygen transfer species of both O(2)-derived atoms to triphenylphosphine and a nucleophilic alkene such as 2,3-dimethyl-2-butene in both HFIP and acetonitrile. UV-vis spectroscopy combined with the measured stoichiometry of PPh(3):O(2) = approximately 2 in a catalytic oxidation of PPh(3) suggests a dioxygenase type activation of O(2) with structural identification of the O-O bond cleavage reaction step, formation of Ru(2) as an intermediate, and the proof that Ru(2) is a donor of both oxygen atoms.