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.

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.

A cobalt-silyl moiety reveals metal-ligand cooperative group transfer to generate isocyanate from the reaction of alkyl azide and CO. This reaction involves the reversible insertion of a nitrene group into...