A Single Nickel Catalyst for the Acceptorless Dehydrogenation of Alcohols and Hydrogenation of Carbonyl Compounds

Synthesis, Reactivity, and Catalytic Transfer Hydrogenation Activity of Ruthenium Complexes Bearing NNN Tridentate Ligands: Influence of the Secondary Coordination Sphere

By the introduction of -OH group(s) into different position(s) of 6-(pyridin-2-ylmethyl)-2,2'-bipyridine, several NNN-type ligands were synthesized and then introduced to ruthenium (Ru) centers by reactions with RuCl2(PPh3)3. In the presence of PPh3 or CO, these ruthenium complexes reacted with NH4PF6 in CH2Cl2 or CH3OH to give a series of ionic products 5-9. The reaction of Ru(L2)(PPh3)Cl2 (2) with CO generated a neutral complex [Ru(L2)(CO)Cl2] (10). In the presence of CH3ONa, 10 was further converted into complex [Ru(L2)(HOCH3)(CO)Cl] (11), in which there was a methanol molecule coordinating with ruthenium, as suggested by density functional theory calculations. The catalytic transfer hydrogenation activity of all of these new bifunctional metal-ligand complexes was tested. Dichloride complex 2 exhibits best activity, whereas carbonyl complexes 10 and 11 are efficient for selectively reducing 5-hexen-2-one, suggesting different hydrogenation mechanisms. The results reveal the dramatic influence for the reactivity and catalytic activity of the secondary coordination sphere in transition metal complexes.

Phosphine-pyridonate ligands containing octahedral ruthenium complexes: access to esters and formic acid

Selective formation of esters from primary alcohols or formic acid from carbon dioxide was achieved in the presence of phosphine-pyridone containing ruthenium catalysts.

Second sphere ligand modifications enable a recyclable catalyst for oxidant-free alcohol oxidation to carboxylates

Ruthenium–terpyridine complexes appended with secondary amines impart hydride stability and recyclability toward catalytic dehydrogenative alcohol oxidation to carboxylates.

1,3-N,O-Complexes of late transition metals. Ligands with flexible bonding modes and reaction profiles

1,3-N,O-Chelating ligands are ubiquitous in nature owing to their occurrence as α-chiral amino acids in metalloproteins.

Acceptorless dehydrogenation and dehydrogenative coupling of alcohols catalysed by protic NHC ruthenium complexes

A new family of protic NHC Ru complexes can serve as efficient catalysts for acceptorless dehydrogenative transformations of alcohols.

Ni(ii)–N′NN′ pincer complexes catalyzed dehydrogenation of primary alcohols to carboxylic acids and H2accompanied by alcohol etherification

Ni(L)catalyzed acceptorless dehydrogenation of alcohol/alkoxide to carboxylate with H₂liberation.

Dehydrogenation of benzyl alcohol with N2O as the hydrogen acceptor catalyzed by the rhodium(i) carbene complex: insights from quantum chemistry calculations

The detailed mechanisms of the dehydrogenation of benzyl alcohol with N₂O as the hydrogen acceptor catalyzed by the rhodium(i) carbene complex for the formation of the corresponding carboxylic acid or ester have been investigated via density functional theory (DFT) calculations at the M06 level of theory. Three cycles were considered for the formation of benzaldehyde, benzyl benzoate and benzoic acid. On the basis of the calculations, the rate-determining step for these three cycles is involved in N₂O activation by the rhodium ammine hydride complex with an activation barrier of only 22.6 kcal mol^-1, which is different from the previous mechanism proposed by Gianetti and co-workers, where the hydride is transferred from the Rh atom to the oxygen atom of N₂O with a barrier of 30.5 kcal mol^-1. In addition, the calculations also demonstrated that one more N₂O is necessary to give benzoic acid, and the reaction can only take place under anhydrous conditions. Present calculations are in good agreement with the experimental observations and provide new insights into the dehydrogenation of benzyl alcohol with N₂O as the hydrogen acceptor.

Acetals from primary alcohols with the use of tridentate proton responsive phosphinepyridonate iridium catalysts

The association of the new phosphinepyridonate ligands along with an iridium metallic precursor resulted in the selective acetalization of various primary alcohols via a formal dehydrogenative coupling reaction.