The syntheses and characterization of alkali metal complexes of an unsymmetrical monoanionic imidazolin-2-imino–phosphanamidinate ligand, {NHIDippP(Ph)N(Dipp)}− {L}− [Dipp = 2,6-diisopropylphenyl] is reported. The protio-ligand [NHIDippP(Ph)NH(Dipp)] (LH) was obtained by the reaction of N-heterocyclic imine (NHI) and [PhP(Cl)NHDipp] in the presence of Et3N in toluene at room temperature. The lithium complex [{NHIDippP(Ph)N(Dipp)}Li(OEt2)] (1) (Et = ethyl) was synthesized by the reaction of the protio ligand LH and one equivalent LiCH2SiMe3 in diethyl ether at room temperature. The reaction of sodium or potassium hexamethyldisilazide [MN(SiMe3)2] (M = Na or K) with LH in 1:1 molar ratio yielded corresponding alkali metal complexes [{NHIDippP(Ph)N(Dipp)}Na(THF)] (2) and [{NHIDippP(Ph)N(Dipp)}K(THF)2] (3) respectively in good yield. The molecular structures of the protio-ligand LH and alkali metal complexes 1 and 3 were established by single-crystal X-ray diffraction analysis. In the solid-state structures of 1 and 3, the lithium and potassium ions are κ2 bonded to the monoanionic ligand moiety through the imine nitrogen and phosphanamidinate nitrogen atoms. © 2021 Elsevier B.V.