Amide‐zing: The reaction between 2 equivalents of Ph2P(CH2)2NH2 and cis‐Ru(CH3CN)2(η3‐C3H5)(cod)BF4 (cod=1,5‐cyclooctadiene) forms a highly active catalyst precursor for the selective hydrogenation ...of amides. The reaction proceeds with excellent atom economy, yield, and turnover numbers (TONs) under moderate reaction conditions. The technology offers a greener, practical approach to the use of metal hydride reagents commonly employed in both academia and industry.
The electrolysis of water to form hydrogen and oxygen is a promising method to store renewable energy. This method requires electrodes that convert water into protons, electrons, and oxygen. We ...report a multifunctional polymer that conducts electrons and ions and may coreact with the electrocatalyst in the oxygen evolution reaction (OER). The electrodes were prepared in two steps from off-the-shelf reagents. They operate with low loadings of abundant catalysts and are among the most active (100 mA cm–2 at 1.43 V vs RHE (1.41 V, iR-corrected)) and stable electrodes, reported to date under harsh conditions (85 °C, 6 M KOH, 120 h (0.69% loss over the first 14.5 h and then 0.61% loss over 105.5 h)). Control experiments on glassy carbon electrodes showed that the polycarbazole system significantly outperformed a Nafion system of the same catalyst loading. This simple strategy can be applied to other types of electrodes.
The organic carbazole–cyanobenzene push–pull dye 1,2,3,5-tetrakis(carbazol-9-yl)-4,6-dicyanobenzene was derivatized and attached to carbon or indium-doped tin oxide (ITO) electrodes by simple ...diazonium electrografting. The surface-bound dye is active and stable for the visible light photosynthetic isomerization of a wide range of functionalized stilbene and cinnamic acid derivatives. Up to 87,000 net turnovers were obtained for the isomerization of trans-stilbene. The isomerizations can be carried out in air with a 33% reduction in the rate. The ITO photoelectrodes are also active and stable toward photo-oxidations under basic and acidic conditions.
The bifunctional addition of lactones/esters is unexpectedly facile at low temperatures. Catalytic hydrogenations of esters can be carried out under mild conditions, e.g. −20 °C under 4 atm of H2, ...but product inhibition slows these reactions over time.
A series of Ir1–x Cu x (x = 0–0.5) hydrous oxide nanoparticles (HO-np) were prepared simply by stirring solutions of IrCl3 hydrate and CuCl2 hydrate in aqueous KOH under air. Their water oxidation ...activities were measured in 0.1 M HClO4. The Ir0.89Cu0.11 HO-np was the most active catalyst in the series with mass (Ir) – normalized activity = 142 A gIr –1 and electrochemically accessible Ir sites normalized activity >180 A mmolIr –1 (both at 250 mV overpotential). The Ir0.89Cu0.11 HO-nps were stable for 24 h galvanostatic oxidations at 1 mA cm–2 geometric, with only 280 mV overpotential. The average diameter of the Ir0.89Cu0.11 HO-nps was ∼1.30 nm. XPS results suggested that doping with Cu2+ reduces the overall charge in the lattice, resulting in higher electron density at Ir than in pure Ir HO-np. Preliminary mechanistic investigations showed that the activity enhancement by Cu is not only a surface area effect, and the presence of Cu does not appear to significantly alter the mechanism of the water oxidation reaction.
The catalytic intermediate trans-Ru((R)-BINAP)(H)2((R,R)-dpen) (1) reacted on mixing with acetophenone in THF at −80 °C under ∼2 atm H2 to generate the alkoxide ...trans-Ru((R)-BINAP)(H)((Ph)(Me)CHO)((R,R)-dpen) (6). Contrary to expectations, free Ru-amide and 1-phenylethanol were not the immediate products of this addition reaction. The addition reaction was reversible in THF. 2-Propanol prevents racemization of the alcohol product in THF solvent.
The transition state for the metal–ligand bifunctional addition step in Noyori’s enantioselective ketone hydrogenation was investigated using intramolecular trapping experiments. The bifunctional ...addition between the Ru dihydride trans-Ru((R)-BINAP)(H)2((R,R)-dpen) and the hydroxy ketone 4-HOCH2C6H4(CO)CH3 at −80 °C exclusively formed the corresponding secondary ruthenium alkoxide trans-Ru((R)-BINAP)(H)(4-HOCH2C6H4CH(CH3)O)((R,R)-dpen). Combined with the results of control experiments, this observation provides strong evidence for the formation of a partial Ru–O bond in the transition state.
The catalyst system trans-Ru(H)2(1R,2R)-N,N-bis{2-bis(3,5-dimethylphenyl)phosphinobenzyl}cyclohexane-1,2-diamine, NaOEt, in DME or THF solvent hydrogenates a series of functionalized racemic ...esters under mild conditions with dynamic kinetic resolution with up to 100% conversion, 95% enantiomeric excess, and 1000 turnovers. A preliminary mechanistic study reveals that several exchange and scrambling processes occur during the hydrogenation.
The dihydrogen compound trans-Ru((R)-BINAP)(H)(η2-H2)((R,R)-dpen)+ (2‘, BINAP = 2,2‘-bis(diphenylphosphino)-1,1‘-binaphthyl, dpen = 1,2-diphenylethylenediamine) is a proposed intermediate in ...asymmetric ketone hydrogenations. It quickly reacts at −80 °C with 1 equiv of the base KO t Bu in 2-PrOH-d 8/CH2Cl2-d 2 under H2 to generate trans-Ru((R)-BINAP)(H)(2-PrO)((R,R)-dpen) (4). The alkoxide 4 does not react with H2 after hours under ambient conditions. Addition of 1 equiv of KO t Bu to 4 produces a hydrogen bonded species 10 that reacts readily with H2 at −80 °C to generate the dihydride catalytic intermediate trans-Ru((R)-BINAP)(H)2((R,R)-dpen) (3‘). Addition of 1 equiv of ((CH3)3Si)2NK to the alkoxide 4 produces the amide catalytic intermediate 5. Compound 5 reacts reversibly with H2 to generate 3‘.
High-throughput screening and lab-scale optimization were combined to develop the catalytic system trans-RuCl2((S,S)-skewphos)((R,R)-dpen), 2-PrONa, and 2-PrOH. This system hydrogenates ...functionalized α-phenoxy and related amides at room temperature under 4 atm H2 pressure to give chiral alcohols with up to 99% yield and in greater than 99% enantiomeric excess via dynamic kinetic resolution.
