The oxidation of alkenes, alkanes, and alcohols with H 2 O 2 is catalyzed efficiently using an in situ prepared catalyst comprised of a Mn II salt and pyridine-2-carboxylic acid (PCA) together with a ketone in a wide range of solvents. The mechanism by which these reactions proceed is elucidated, with a particular focus on the role played by each reaction component: i.e., ketone, PCA, Mn II salt, solvent, etc. It is shown that the equilibrium between the ketone cocatalysts, in particular butanedione, and H 2 O 2 is central to the catalytic activity observed and that a gem-hydroxyl-hydroperoxy species is responsible for generating the active form of the manganese catalyst. Furthermore, the oxidation of the ketone to a carboxylic acid is shown to antecede the onset of substrate conversion. Indeed, addition of acetic acid either prior to or after addition of H 2 O 2 eliminates a lag period observed at low catalyst loading. Carboxylic acids are shown to affect both the activity of the catalyst and the formation of the gem-hydroxyl-hydroperoxy species. The molecular nature of the catalyst itself is explored through the effect of variation of Mn II and PCA concentration, with the data indicating that a Mn II :PCA ratio of 1:2 is necessary for activity. A remarkable feature of the catalytic system is that the apparent order in substrate is 0, indicating that the formation of highly reactive manganese species is rate limiting.

The potentially tridentate ligand bis[(1-methyl-2-benzimidazolyl)ethyl]amine ( 2BB ) was employed to prepare copper complexes [( 2BB )Cu I ]OTf and [( 2BB )Cu II (H 2 O) 2 ](OTf) 2 as bioinspired models of lytic polysaccharide copper-dependent monooxygenase (LPMO) enzymes. Solid-state characterization of [( 2BB )Cu I ]OTf revealed a Cu(I) center with a T-shaped coordination environment and metric parameters in the range of those observed in reduced LPMOs. Solution characterization of [( 2BB )Cu II (H 2 O) 2 ](OTf) 2 indicates that [( 2BB )Cu II (H 2 O) 2 ] 2+ is the main species from pH 4 to 7.5; above pH 7.5, the hydroxo-bridged species [{( 2BB )Cu II (H 2 O) x } 2 (μ-OH) 2 ] 2+ is also present, on the basis of cyclic voltammetry and mass spectrometry. These observations imply that deprotonation of the central amine of Cu(II)-coordinated 2BB is precluded, and by extension, amine deprotonation in the histidine brace of LPMOs appears unlikely at neutral pH. The complexes [( 2BB )Cu I ]OTf and [( 2BB )Cu II (H 2 O) 2 ](OTf) 2 act as precursors for the oxidative degradation of cellobiose as a cellulose model substrate. Spectroscopic and reactivity studies indicate that a dicopper(II) side-on peroxide complex generated from [( 2BB )Cu I ]OTf/O 2 or [( 2BB )Cu II (H 2 O) 2 ](OTf) 2 /H 2 O 2 /NEt 3 oxidizes cellobiose both in acetonitrile and aqueous phosphate buffer solutions, as evidenced from product analysis by high-performance liquid chromatography-mass spectrometry. The mixture of [( 2BB )Cu II (H 2 O) 2 ](OTf) 2 /H 2 O 2 /NEt 3 results in more extensive cellobiose degradation. Likewise, the use of both [( 2BB )Cu I ]OTf and [( 2BB )Cu II (H 2 O) 2 ...

Fully reversible photoswitching of the coordination mode of the ligand MeN4Py (1,1-di(pyridin-2-yl)-N,N'-bis(pyridin-2-yl-methyl)-ethan-1-amine) in its ruthenium(II) complex with visible light is reported. Irradiation with visible light results in dissociation of a pyridyl moiety, which is reversed by irradiation at 355 nm.

No abstract