A terminal nickel(II) anilide complex featuring an unsymmetrically substituted amido pincer ligand: synthesis and reactivity

This work describes preparation and reaction chemistry of a terminal nickel(II) anilide complex supported by an unsymmetrically substituted diarylamido diphosphine ligand, N(o-C(6)H(4)PPh(2))(o-C(6)H(4)P(i)Pr(2))](-) (Ph-PNP-(i)Pr](-)). Treatment of NiCl(2)(DME) with HPh-PNP-(i)Pr] in THF at room temperature produced Ph-PNP-(i)Pr]NiCl as green crystals in 82% yield. Salt metathesis of Ph-PNP-(i)Pr]NiCl with LiNHPh(THF) in THF at -35 °C generated cleanly Ph-PNP-(i)Pr]NiNHPh as a greenish blue solid. The anilide complex deprotonates protic (e.g., PhOH and PhSH) and aprotic (e.g., trimethylsilylacetylene, phenylacetylene, and acetonitrile) acids in benzene at room temperature to give quantitatively Ph-PNP-(i)Pr]NiX (X = OPh, SPh, C≡CSiMe(3), C≡CPh, CH(2)CN). In addition, Ph-PNP-(i)Pr]NiNHPh also behaves as a nucleophile to react with acetyl chloride to yield Ph-PNP-(i)Pr]NiCl and N-phenylacetamide quantitatively. Carbonylation of Ph-PNP-(i)Pr]NiNHPh with carbon monoxide affords cleanly the carbamoyl derivative Ph-PNP-(i)Pr]NiC(O)NHPh]. The relative bond strengths of Ni-E in Ph-PNP-(i)Pr]NiEPh (E = NH, O, S, C≡C) are assessed and discussed.