Monomeric nickel hydroxide stabilized by a sterically demanding phosphorus–nitrogen PN3P-pincer ligand: synthesis, reactivity and catalysis

Abstract

A terminal nickel hydroxide complex (PN³P)Ni(OH) (3) bearing the 2^nd generation phosphorus–nitrogen PN³P-pincer ligand has been synthesized and structurally characterized. As a nucleophile, 3 reacts with CO to afford the hydroxycarbonyl complex 4, (PN³P)Ni(COOH). 3 can also activate CO₂ and CS₂ to produce nickel bicarbonate (PN³P)Ni(OCOOH) (5) and bimetallic dithiocarbonate [(PN³P)NiS]₂CO (6) respectively, as well as to promote aryl isocyanate and isothiocyanate insertion into the Ni–OH bond to give the corresponding (PN³P)NiEC(O)NHAr complexes (E = O, 7; E = S, 8). In addition, 3 catalyzes the nitrile hydration to various amides with well-defined intermediates (PN³P)Ni–NHC(O)R (R = Me, 9; R = Ph, 10).