Asuka Matsunami

Enhanced Hydrogen Generation from Formic Acid by Half‐Sandwich Iridium(III) Complexes with Metal/NH Bifunctionality: A Pronounced Switch from Transfer Hydrogenation

By switching the catalytic function from transfer hydrogenation based on the metal/NH bifunctionality, facile dehydrogenation of formic acid was achieved by amido- and hydrido(amine)-Ir complexes derived from N-triflyl-1,2-diphenylethylenediamine (TfDPEN) at ambient temperature even in the absence of base additives. Further acceleration was observed by the addition of water, leading to a maximum turnover frequency above 6000 h(-1). A proton-relay mechanism guided by the protic amine ligand and water is postulated for effective protonation of metal hydrides.

Protic NNN and NCN Pincer‐Type Ruthenium Complexes Featuring (Trifluoromethyl)pyrazole Arms: Synthesis and Application to Catalytic Hydrogen Evolution from Formic Acid

NNN and NCN pincer-type ruthenium(II) complexes featuring two protic pyrazol-3-yl arms with a trifluoromethyl (CF3 ) group at the 5-position were synthesized and structurally characterized to evaluate the impact of the substitution on the properties and catalysis. The increased Brønsted acidity by the highly electron-withdrawing CF3 pendants was demonstrated by protonation-deprotonation experiments. By contrast, the IR spectra of the carbonyl derivatives as well as the cyclic voltammogram indicated that the electron density of the ruthenium atom is negligibly influenced by the CF3 group. Catalysis of these complexes in the decomposition of formic acid to dihydrogen and carbon dioxide was also examined. The NNN pincer-type complex 1 a with the CF3 group exhibited a higher catalytic activity than the tBu-substituted analogue 1 b. In addition, the bis(CF3 -pyrazolato) ammine derivative 4 catalyzed the reaction even in the absence of base additives.

Synthesis of Multisubstituted Azatriphenylenes by Iridium-Catalyzed [2 + 2 + 2] Cycloaddition of Biaryl-Linked Diynes with Nitriles

A convenient synthesis of multisubstituted azatriphenylenes is reported. [Ir(cod)Cl]2/diphosphine is an efficient catalyst for the [2 + 2 + 2] cycloaddition of biaryl-linked diynes with nitriles to give multisubstituted azatriphenylenes in high yields. Aromatic, heteroaromatic, aliphatic, and functionalized nitriles could be used for the reaction.

Accessible Bifunctional Oxy-Tethered Ruthenium(II) Catalysts for Asymmetric Transfer Hydrogenation

A concise synthesis of new oxy-tethered ruthenium complexes effective for the asymmetric transfer hydrogenation of aromatic ketones is described. The oxy-tether was constructed via a defluorinative etherification arising from an intramolecular nucleophilic substitution of a perfluorinated phenylsulfonyl substituent. The obtained tethered complexes exhibited desirable catalytic activity and selectivity, especially in the asymmetric transfer hydrogenation of functionalized aromatic ketones. The robustness and rigidity of the tether contribute to their superior catalytic performance relative to the nontethered prototype complex.

Synthesis of Chiral Homoallylic Nitriles by Iridium-Catalyzed Allylation of Cyanoacetates

A synthesis of chiral homoallylic nitriles by the iridium-catalyzed allylation of cyanoacetates followed by Krapcho demethoxycarbonylation has been developed. A wide range of homoallylic nitriles were obtained with a high enantioselectivity (>95-99% ee). These compounds are useful chiral building blocks because further synthetic elaboration starting from a nitrile or terminal alkene is possible.