The phosphinoimino-2-imidazoline 4 was synthesized by a salt elimination reaction between LiNIPr [NIPr = 1,3-bis(2,6-(diisopropylphenyl)imidazolin-2-ylidenamino)] and 2-chloro-1,3,2-diazaphospholene. DFT study revealed that the HOMO of 4 involves the lone pair orbitals on the P atom and the N atom at the exocyclic P–N bond. Compound 4 displays selectivity in coordinating to acids. Thus, the N atom at the exocyclic P–N bond coordinates to a hard acid (HCl) which eventually led to the cleavage of the P–N bond, while the central P atom forms a dative bond with a soft Lewis acid, BH3. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim