Reactions of tBuP(NH2)2 with Group 13 trialkyls MR3 (M = Al, Ga, In; R = Me, tBu) were investigated in detail. According to variable-temp. (VT) NMR investigations, the reaction proceeds stepwise with the initial formation of aminophosphane adducts, which subsequently react to give iminophosphorane adducts and finally the heterocyclic metallonitridophosphinates. BP86/TZVPP (DFT) calcns. were performed to verify this reaction pathway, to, elucidate the influence of the central Group 13 element on the stability of the reaction intermediates and the heterocycles, as well as to assess the thermodn. of their formation. The relative stability of free and complexed aminophosphane RP(NH2)2 and iminophosphorane R(H2N)(H)P:NH (adducts) with PIII and PV centers was studied in more detail with DFT and MP2 methods. In addn., the influence of the substituent R was investigated by variation of R from H to Me, tBu, F, and NH2. In general, the aminophosphane form was favored for the free ligand, however, upon complexation with MR3 (M = Al, Ga; R = alkyl) both forms are almost equal in energy. [on SciFinder (R)]