Synthesis of New Ruthenium‐CAP Complexes and Use as Catalysts for Benzonitrile Hydration to Benzamide

Electrosynthesis of Amides through Cu- and Co-Incorporated Nickel Hydroxide-Catalyzed Oxidation of Primary Amines Coupled with Hydrogen Evolution

The electrocatalytic oxidation of organic molecules coupled with hydrogen evolution reaction can reduce overpotential and can be connected in series with nonelectrochemical processes to achieve the preparation of more high-value compounds. Herein, Cu- and Co-incorporated nickel hydroxide (CuCo-Ni(OH)2) was synthesized and applied to the anodic benzylamine oxidation reaction, which is 280 mV lower than the corresponding oxygen evolution reaction to reach the current density of 50 mA cm-2. When the electrocatalytic oxidation of benzylamine and hydrogen evolution reaction are coupled to form an electrolytic cell, the potential to reach 10 mA cm-2 is reduced by 197 mV compared to the overall water splitting. The benzylamine is converted to benzamide with 99.3% conversion and 90.2% faraday efficiency under 1.45 V constant voltage electrolysis, and the catalytic performance remains at a high level after 4 cycles. The characterization and density functional theory calculations show that Cu and Co share the transfer charge from Ni, making it easy for CuCo-Ni(OH)2 to deprotonate Ni-O* sites. The formed Ni-O* sites exhibit lower energy barriers in the proton transfer of benzylamine to benzonitrile and hydration intermediates, resulting in a better catalytic performance of CuCo-Ni(OH)2 than Ni(OH)2 in the electrocatalytic oxidation of benzylamine to benzamide.

Hydration of Nitriles Catalyzed by Ruthenium Complexes: Role of Dihydrogen Bonding Interactions in Promoting Base-Free Catalysis

Ru(II) complexes of amide-phosphine-based tridentate ligands additionally containing pyridine, isoquinoline, and quinoline rings have been synthesized, and their catalytic utility for the selective hydration of nitriles to amides is explored under the base-containing as well as base-free conditions. The chloride-ligated complexes 1-3 exhibited significant catalytic activity in the presence of a base, whereas hydride-ligated complexes 4-6 carried out the hydration of nitrile without the requirement of any base. The mechanistic studies revealed the involvement of [Ru-H] species as the active catalyst in the catalytic cycle. The [Ru-H] species assisted in the polarization of an incoming water molecule through [Ru-H···H-OH] dihydrogen bonding interaction and consequently aided in the attack of a positioned water molecule to a nitrile coordinated to a ruthenium center. Substrate binding studies and kinetic experiments further supported the mechanism. A wide variety of aromatic nitriles containing both electron-withdrawing and electron-releasing groups as well as other substrates including aliphatic nitriles, base-sensitive nitriles, and a few biologically relevant nitriles were employed for the selective hydration.