The effects of pyridine substituents (Y) on the Ru (VI) compounds RuO2Cl2(Y-pyridine), and RuO(2)Cl(2)Z (Z =bipyridine, phenanthroline)

The compounds RuO2Cl2(Y-py)(2) 1 (py = pyridine, Y = H 1a, 4-t-Bu 1b, 3-CN 1c, 4-CN 1d, 2-Br 1e, 3-Br 1f, 4-Br 1g, 4-Cl 1h, 4-Me 1i, 4-C(O)C6H5 1j, 3- COOH 1k, 4-COOH 1I) and RuO(2)Cl(2)Z 2 (Z = bipyridine 2a, phenanthroline 2 b) were prepared and the effects of the various substituents on the propert ies of the compounds were investigated, including their ability to oxidise 1-hexanol to hexanal, both stoichiometrically and catalytically. The positi on of the v(Ru=O) bands of complexes 1 correlate with the Hammett sigma(1) (or Taft sigma*) and Pauling-type electronegativity values of the substitue nts on the pyridine ring. Identical trends due to the substituents were obs erved for both the stoichiometric and catalytic oxidations.