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

A series of nickel(ii) complexes of the type R-PNP]Ni(ER') (R-PNP](-) = N(o-C(6)H(4)PR(2))(2)](-); R = Ph, (i)Pr, Cy; E = NH, O, S; R' = Ph, (t)Bu) featuring unsupported, covalently bound pi-donor ligands have been prepared and characterized. The metathetical reactions of R-PNP]NiCl (R = Ph, (i)Pr, 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(t)Bu or NaO(t)Bu generated tert-butyl amide Ph-PNP]Ni(NH(t)Bu) and tert-butoxide Ph-PNP]Ni(O(t)Bu), respectively. In contrast, attempts to prepare analogous tert-butyl amide and tert-butoxide complexes of (i)Pr-PNP](-) or Cy-PNP](-) were not successful. Protonolysis studies of these nickel(ii)-heteroatom complexes revealed the basic reactivity of these pi-donor ligands. The basicity follows the order NH(t)Bu > O(t)Bu > NHPh > OPh > SPh. In addition to solution NMR spectroscopic data for all new compounds, X-ray structures of (i)Pr-PNP]Ni(NHPh) and (i)Pr-PNP]Ni(OPh) are presented.