A bis(arylphosphinito)amide pincer ligand that binds nickel forming six-membered metallacycles

The synthesis of a bis(arylphosphinito)amide pincer ligand P₂ONO⁻ designed to form two six-membered rings upon metallation is reported. Phosphination of a known bis(phenolato)amide ONO³⁻ scaffold led to isolation of two isomers: the intended H(P₂ONO) preligand with an amine moiety is formed as a kinetic product, which isomerizes via net oxidative addition of the amine N−H to phosphorous to yield a benzoxazaphosphole-containing thermodynamic product. Both isomers undergo productive metallation with NiBr₂(dimethoxyethane) to produce the same complex, (P₂ONO)NiBr. Treatment with triethylborohydride furnished the terminal hydride complex (P₂ONO)NiH. The bromide and hydride complexes enabled comparisons of the steric and electronic properties of the P₂ONO⁻ ligand with other amide-based pincers.