Theoretical Study of Oxidation of Cyclohexane Diol to Adipic Anhydride by [RuIV(O)(tpa)(H2O)]2+ Complex (tpa ═ Tris(2-pyridylmethyl)amine)

Effects of Methyl Substitution in Ruthenium Tris(2-pyridylmethyl)amine Photocaging Groups for Nitriles

Four complexes of the general formula [Ru(L)(CH3CN)2](PF6)2, [L = TPA (5), MeTPA (6), Me2TPA (7), and Me3TPA (8)] [TPA = tris[(pyridin-2-yl)methyl]amine, where methyl groups were introduced consecutively onto the 6-position of py donors of TPA, were prepared and characterized by various spectroscopic techniques and mass spectrometry. While 5 and 8 were isolated as single stereoisomers, 6 and 7 were isolated as mixtures of stereoisomers in 2:1 and 1.5:1 ratios, respectively. Steric effects on ground state stability and thermal and photochemical reactivities were studied for all four complexes using (1)H NMR and electronic absorption spectroscopies and computational studies. These studies confirmed that the addition of steric bulk accelerates photochemical and thermal nitrile release.

Mechanistic study of methanol oxidation by RuIV–oxo complexes

The catalytic conversion of methanol to formaldehyde by three kinds of non-porphyrin Ru complexes, Ru IV O ( TPA ) (TPA = tris(2-pyridylmethyl)amine) (1a), Ru IV O (6- COO - TPA ) (6-COO-TPA = 2-(6-carboxyl-pyridyl)methyl-bis(2-pyridylmethyl)amine) (1b), and Ru IV O ( N4Py ) (N4Py = N,N-bis(2-pyridyl-methyl)-N-bis(2-pyridyl)methylamine) (1c), is discussed by using density functional theory (DFT) calculations. There are two possible reaction pathways for the oxidation of methanol to formaldehyde with respect to the first hydrogen abstraction from the methyl group (path 1) and the hydroxyl group (path 2). Path 1 and path 2 involve the hydroxymethyl radical (• CH 2 OH ) and the methoxyl radical ( CH 3 O •), respectively, as an intermediate. DFT calculations demonstrate that the two pathways are energetically comparable in the reactions by the three Ru IV –oxo complexes. The reactions with 1a and 1c are initiated by the C – H bond dissociation with activation barriers of 22.2 and 21.4 kcal/mol, respectively, while the reaction with 1b is initiated by the O – H bond dissociation with an activation barrier of 18.1 kcal/mol. However, the calculations showed that the rate-determining step is the H -atom abstraction from the CH 3 group of methanol in all the pathways. These results are in good agreement with kinetic analysis of the reactions by the Ru IV –oxo complexes, being useful for considering the mechanism of methanol oxidation.

Syntheses and properties of phosphine-substituted ruthenium(ii) polypyridine complexes with nitrogen oxides

The substitution lability of the nitrogen oxide ligands of novel phosphine-substituted ruthenium(ii) polypyridine complexes is discussed in comparison with that of the corresponding acetonitrile complexes.

Hydrogen atom abstraction reactions independent of C–H bond dissociation energies of organic substrates in water: significance of oxidant–substrate adduct formation

Adduct formation between Ru(iv)–oxo complexes and substrates with hydrogen bonding affords condensed transition states for substrate oxidations in water.