Cooperativity‐Driven Reactivity of a Dinuclear Copper Dimethylglyoxime Complex

In this report, we present the dinuclear copper(II) dimethylglyoxime (H$_2$dmg) complex [Cu$_2$(H$_2$dmg)(Hdmg)(dmg)]$^+$ (1), which, in contrast to its mononuclear analogue [Cu(Hdmg)$_2$] (2), is subject to a cooperativity-driven hydrolysis. The combined Lewis acidity of both copper centers increases the electrophilicity of the carbon atom in the bridging μ$_2$-O−N=C-group of H$_2$dmg and thus, facilitates the nucleophilic attack of H2O. This hydrolysis yields butane-2,3-dione monoxime (3) and NH$_2$OH that, depending on the solvent, is then either oxidized or reduced. In ethanol, NH$_2$OH is reduced to NH$_4$$^+$, yielding acetaldehyde as the oxidation product. In contrast, in CH$_3$CN, NH$_2$OH is oxidized by Cu$^{II}$ to form N$_2$O and [Cu(CH$_3$CN)4]$^+$. Herein are presented the combined synthetic, theoretical, spectroscopic and spectrometric methods that indicate and establish the reaction pathway of this solvent-dependent reaction

Mechanistic and kinetic investigations of on/off (photo)switchable binding of carbon monoxide by chromium(0), molybdenum(0) and tungsten(0) carbonyl complexes with a pyridyl‐mesoionic carbene ligand

This work tackles the photochemistry of a series of mononuclear Cr0, Mo0 and W0 carbonyl complexes containing a bidentate mesoionic carbene ligand of the 1,2,3‐triazol‐5‐ylidene type. FTIR spectroscopy, combined with density functional theory calculations, revealed a clean photo‐induced reaction in organic solvents (acetonitrile, pyridine, valeronitrile) to give mainly one photoproduct with monosubstitution of a carbonyl ligand for a solvent molecule. The highest photodissociation quantum yields were reached for the Cr0 complex under UV irradiation (266 nm). Based on previous investigations, the kinetics of the dark reverse reactions have now been determined, with reaction times of up to several hours in pyridine. Photochemical studies in the solid state (KBr matrix, frozen solution) also showed light‐induced reactivity with stabilization of the metastable intermediate with a free coordination site at very low temperature. The identified reactive species emphasizes a mechanism without ligand–sphere reorganization.Deutsche Forschungsgemeinschaf