Terminal nickel(ii) amide, alkoxide, and thiolate complexes containing amido diphosphine ligands of the type [N(o-C6H4PR2)2]− (R = Ph, iPr, Cy)

Abstract

A series of nickel(II) complexes of the type [R-PNP]Ni(ER′) ([R-PNP]⁻ = [N(o-C₆H₄PR₂)₂]⁻; R = Ph, ⁱPr, Cy; E = NH, O, S; R′ = Ph, ^tBu) featuring unsupported, covalently bound π-donor ligands have been prepared and characterized. The metathetical reactions of [R-PNP]NiCl (R = Ph, ⁱPr, Cy) with LiNHPh, NaOPh, or NaSPh, respectively, produced the corresponding anilide [R-PNP]Ni(NHPh), phenolate [R-PNP]Ni(OPh), and thiophenolate [R-PNP]Ni(SPh) derivatives. Treatment of [Ph-PNP]NiCl with either LiNH^tBu or NaO^tBu generated tert-butyl amide [Ph-PNP]Ni(NH^tBu) and tert-butoxide [Ph-PNP]Ni(O^tBu), respectively. In contrast, attempts to prepare analogous tert-butyl amide and tert-butoxide complexes of [ⁱPr-PNP]⁻ or [Cy-PNP]⁻ were not successful. Protonolysis studies of these nickel(II)–heteroatom complexes revealed the basic reactivity of these π-donor ligands. The basicity follows the order NH^tBu > O^tBu > NHPh > OPh > SPh. In addition to solution NMR spectroscopic data for all new compounds, X-ray structures of [ⁱPr-PNP]Ni(NHPh) and [ⁱPr-PNP]Ni(OPh) are presented.