The reaction of a nickel(i) carbonyl species with CH3I revealed the formation of (PNP)NiCOCH3 which differs from its zerovalent congener.

Reversible transformations are observed between a phosphide-nickel(II) alkoxide and a phosphinite-nickel(0) species via a P-O bond formation coupled with a 2-e(-) redox change at the nickel center. In the forward reaction, the nickel(0) dinitrogen species (PP(OMe)P)Ni(N2) (2) and {(PP(OMe)P)Ni}2(μ-N2) (3) were formed from the reaction of (PPP)NiCl (1) with a methoxy anion. In the backward reaction, a (PPP)Ni(II) moiety was regenerated from the CO2 reaction of 3 with the concomitant formation of a methyl carbonate ligand in (PPP)Ni(OCOOMe) (7). Thus, unanticipated metal-ligand cooperation involving a phosphide based ligand is reported.

P–S bond formation/cleavage mediated by a nickel ion supported by a PPP ligand (PPP = P­[2-P i Pr2-C6H4]2 –) has been investigated herein. To gain an entry into this chemistry, a mononuclear thiolato nickel complex, (PPP)­Ni­(SAr) (1a,b) was prepared by treating the chloride starting material with NaSPh. Upon carbonylation, this complex produces a nickel(0) monocarbonyl species, (PPSArP)­Ni­(CO) (2a,b), in which the thiolate migrates onto the central P of the ligand to give a P–S bond and two-electron reduction of a nickel­(II) center. The reaction undergoes via a pseudo-first-order decay with respect to consumption of a nickel­(II) thiolato species, suggesting an intramolecular reaction under the excess CO­(g) conditions. The reverse reaction involving P–S bond cleavage with concomitant decarbonylation occurs to regenerate 1a,b in benzene. Reaction of 2a with trityl chloride results in Ph3CSPh formation, whereas the reaction with MeI gives methylation at a phosphide moiety or a thiolate group.

Two pathways of alkoxide migration occurring at a nickel(II) center supported by a PPP ligand (PPP = P[2-PPr-CH]) are presented in this Article. In the first route, the addition of a π-acidic ligand to a (PPP)Ni alkoxide species reveals the formation of a P-O bond. This reaction occurs via metal-ligand cooperation (MLC) involving a 2-electron reduction at nickel. To demonstrate a P-O bond formation, a nickel(II) isopropoxide species (PPP)Ni(OPr) (4) was prepared. Upon addition of a π-acidic isocyanide ligand CNBu, a nickel(0) isocyanide species (PPP)Ni(CNBu) (6b) was generated; P-O bond formation occurred via reductive elimination (RE). When CO is present, migratory insertion (MI) occurs instead. The reaction of 4 with CO(g) results in the formation of (PPP)Ni(COOPr) (5), representing an alternative pathway. The corresponding RE product (PPP)Ni(CO) (6a) can be independently produced from the substitution reaction of {(PPP)Ni}(μ-N) (3) with CO(g). While two different carbonylation pathways in 4 seem feasible, C-O bond forming migratory insertion singly occurs. Regeneration of a (PPP)Ni moiety via a P-O bond cleavage was demonstrated by treating 3 with CO(g). The formation of (PPP)Ni(OCOOPr) (7) clearly shows that an isopropoxide group migrates onto the bound CO ligand, and a P-Ni moiety is regenerated.