Metal-ligand cooperation is a new terminology when both a metal ion and its ligand operate as a reaction center. A “ligand” utilized in the metal-ligand cooperative systems can deliver electron(s), a proton and/or a functional group to assist chemistry occurring at a metal center, while the classical ligand typically works as a spectator. Consequently, metal-ligand cooperation can be utilized as a new synthetic methodology to extend the role of transition metal ions in multi-electron catalytic reactions. Recently, our group reported a new type of metal-ligand cooperation with an anionic PPP ligand (PPP– = –P[2-PiPr2-C6H4]2). The reversible phosphide/phosphinite interconversion of a PPP ligand coupled with a 2-electron redox change of nickel (II and 0) was observed in this system. Here, a (PPP)Ni scaffold revealing unusual formation and activation of a P-P bond will be presented. Several divalent nickel(II) amide species were prepared by the addition of different amido groups to (PPP)NiCl. Interestingly, upon addition of CO(g) to a nickel amido species (PPP)Ni(NHMes), a dimeric nickel(0) species, {(PPP)NiCO}2 possessing a new P-P bond was generated. Further {(PPP)NiCO}2 reacts with H2 to give (PPHP)NiCO revealing both P-P bond formation and cleavage are possible with a (PPP)Ni scaffold. As an example of metal-ligand cooperation, the formation of a P-N bond was accomplished by addition of CO(g) to the solution of (PPP)Ni-NTol2. Further reactivity of nickel(0) species toward various reagents will be discussed in this poster.

Unprecedented metal-ligand cooperation of a (PPP)Ni scaffold: Formation of P-E bonds (E = N or P)

253rd National Meeting (2017)

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