Abstractσ2λ3‐“Push‐pull” iminophosphanes Arf−P=N−R, bearing an electron‐acceptor substituent at phosphorus [Arf = 2,6‐bis(trifluoromethyl)phenyl] and a donor group at nitrogen (R = tBu, NMe2), have been synthesized and characterized by NMR spectroscopy and X‐ray analysis. Density functional calculations [B3LYP/6‐311G(d,p)] have been carried out on different iminophosphanes: HP=NH (1), ArfP=NH (2), ArfP=NSiMe3 (3), ArfP=NtBu (4), HP=NNMe2 (5) and ArfP=NNMe2 (6) in order to determine the electronic effect of the Arf substituent and the influence of the donor group R on the stability of the monomeric species. A comparison of the theoretical results and UV photoelectron spectroscopy data for the iminophosphanes 4 and 6 is presented. Theoretical and experimental data suggest that for all iminophosphanes under investigation the π‐system of the Arf group is almost orthogonal to the πP=N system, preventing any stabilizing interaction between the πP=N and the π*b1(aryl) orbitals previously observed for the ArfPH− anion. Here, the Arf substituent effect is mainly steric. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)