Monomeric nickel hydroxide stabilized by a sterically demanding phosphorus-nitrogen (PNP)-P-3-pincer ligand: synthesis, reactivity and catalysis

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