Metal-ligand cooperation can be utilized as a new synthetic approach to extend the role of transition metal ions in multi-electron catalytic reactions. Various metal complexes with redox noninnocent ligands employing a π-conjugated system such as well-known porphyrin were reported where the redox window of a metal complex is expanded. As a recent example of redox-active ligands, bis(imino)pyridine was utilized to establish various multielectron catalytic reactions. In fact, aromatization/dearomatization is also considered as one of metal-ligand cooperations with employing pyridine- or acridine-based pincer ligand. Since relatively rare examples were reported with a noninnocent phosphine ligand in organometallic chemistry, we are currently working with an anionic PPP ligand (PPP– = –P[2-PiPr2-C6H4]2). A new type of metal-ligand cooperation is established revealing the reversible phosphide/phosphinite interconversion of a PPP ligand coupled with a 2-electron redox change of nickel (II and 0). A series of alkoxides and pi-acidic ligands were employed to study this cooperative reaction. Here, the formation and activation of a P-P bond at a nickel center supported by a PPP ligand will be presented. In order to employ an additional noninnocent ligand, an amido moiety was utilized to generate (PPP)Ni(NHMes). The formation of {(PPP)NiCO}2 was successfully accomplished from the reaction of (PPP)Ni(NHMes) with CO under light. In this reaction, diphenylurea was generated as a side product. A new P-P bond was confirmed by various spectroscopic techniques including X-ray crystallography. Further formation of (PPHP)NiCO was achieved via P-P bond cleavage from the reaction of {(PPP)NiCO}2 with H2. The details of the synthesis and characterization will be discussed in this presentation.

P-P bond formation via unique metal-ligand cooperation

253rd National Meeting (2017)

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