Studies on transition-metal oxo and nitrido complexes. Part 11. New oxo complexes of ruthenium as aerobically assisted oxidants, and the X-ray crystal structure of [Ru2O6(py)4]·3.5H2O

Abstract
The new complexes [Ru2O6L4] [L = 4-t-butylpyridine (4But-py), nicotinic acid (Hnic), isonicotinamide (isna), pyridine-2-carboxylic acid (Hpyca), or ½(2,2′-bipyridyl) (bipy)] have been prepared and the X-ray crystal structure of another member of the series, [Ru2O6(py)]·3.5H2O, determined [triclinic, space group P, a = 7.943(1), b = 8.952(2), c = 9.257(3) Å, α = 98.76(2), β = 95.75(2), γ = 98.08(1)°, Z = 1, R = 0.065]. New complexes are also reported of the types trans-[RuO2L4]2+ [L = Hnic, Hpyca, or pyridine-3,4-dicarboxylic acid (H2pydca)], trans-[RuO2Cl2L2] (L = py, 4But-py or 4-chloropyridine), trans-[RuO2(pyca)2] and trans-[RuO2Cl3L] (L = py, 4But-py, 3-methylpyridine, or 3,4-dimethylpyridine). Vibrational spectra, structures, and reactions of these species are discussed: they function as overall four-electron oxidants (eight-electron in the case of [Ru2O6L4] ), converting primary alcohols into aldehydes and secondary alcohols into ketones, and function catalytically with N-methylmorpholine N-oxide or iodosylbenzene as co-oxidant. The most soluble of them, trans-[Ru2O6(py)4]·3.5H2O, trans-[Ru2O6(4But-py)4], trans-[RuO2(py)4]2+, and trans-[RuO2Cl3(4But-py)], will also effect such oxidation of alcohols with dioxygen as co-oxidant.

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