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 LiNHtBu or NaOtBu generated tert-butyl amide [Ph-PNP]Ni(NHtBu) and tert-butoxide [Ph-PNP]Ni(OtBu), 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 NHtBu > OtBu > 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.