title: Hemilability-Driven Water Activation: A NiIICatalyst for Base-Free Hydration of Nitriles to Amides.
abstract: The NiIIcomplex 1 containing pyridyl- and hydroxy-functionalized N-heterocyclic carbenes (NHCs) is synthesized and its catalytic utility for the selective nitrile hydration to the corresponding amide under base-free conditions is evaluated. The title compound exploits a hemilabile pyridyl unit to interact with a catalytically relevant water molecule through hydrogen-bonding and promotes a nucleophilic water attack to the nitrile. A wide variety of nitriles is hydrated to the corresponding amides including the pharmaceutical drugs rufinamide, Rifater, and piracetam. Synthetically challenging α-hydroxyamides are accessed from cyanohydrins under neutral conditions. Related catalysts that lack the pyridyl unit (i.e., compounds 2 and 4) are not active whereas those containing both the pyridyl and the hydroxy or only the pyridyl pendant (i.e., compounds 1 and 3) show substantial activity. The linkage isomer 1' where the hydroxy group is bound to the metal instead of the pyridyl group was isolated under different crystallization conditions insinuating a ligand hemilabile behavior. Additional pKameasurements reveal an accessible pyridyl unit under the catalytic conditions. Kinetic studies support a ligand-promoted nucleophilic water addition to a metal-bound nitrile group. This work reports a Ni-based catalyst that exhibits functional hemilability for hydration chemistry.
authors.affiliation: Department of Chemistry and Center for Environmental Sciences and Engineering, Indian Institute of Technology Kanpur, Kanpur, 208016, India.
authors.forename: Kuldeep
authors.initials: K
authors.lastname: Singh
authors.affiliation: Department of Chemistry and Center for Environmental Sciences and Engineering, Indian Institute of Technology Kanpur, Kanpur, 208016, India.
authors.forename: Abir
authors.identifier: http://orcid.org/0000-0003-2478-5044
authors.initials: A
authors.lastname: Sarbajna
authors.affiliation: Department of Chemistry and Center for Environmental Sciences and Engineering, Indian Institute of Technology Kanpur, Kanpur, 208016, India.
authors.forename: Indranil
authors.identifier: http://orcid.org/0000-0003-0845-9193
authors.initials: I
authors.lastname: Dutta
authors.affiliation: Department of Chemistry and Center for Environmental Sciences and Engineering, Indian Institute of Technology Kanpur, Kanpur, 208016, India.
authors.forename: Pragati
authors.initials: P
authors.lastname: Pandey
authors.affiliation: Department of Chemistry and Center for Environmental Sciences and Engineering, Indian Institute of Technology Kanpur, Kanpur, 208016, India.
authors.forename: Jitendra K
authors.identifier: http://orcid.org/0000-0002-5689-8863
authors.initials: JK
authors.lastname: Bera
keywords: amides; cooperative effects; hemilability; metal catalysis; water activation