Syntheses, Structures, Bonding and Photoelectron Spectra of “Push‐Pull”‐Substituted P ‐[2,6‐Bis(trifluoromethyl)phenyl]‐σ 2 λ 3 ‐iminophosphanes

σ 2 λ 3 ‐“Push‐pull” iminophosphanes Ar f −P=N−R, bearing an electron‐acceptor substituent at phosphorus [Ar f = 2,6‐bis(trifluoromethyl)phenyl] and a donor group at nitrogen (R = t Bu, NMe 2 ), 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 ), Ar f P=NH ( 2 ), Ar f P=NSiMe 3 ( 3 ), Ar f P=N t Bu ( 4 ), HP=NNMe 2 ( 5 ) and Ar f P=NNMe 2 ( 6 ) in order to determine the electronic effect of the Ar f 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 Ar f group is almost orthogonal to the π P=N system, preventing any stabilizing interaction between the π P=N and the π* b1(aryl) orbitals previously observed for the Ar f PH − anion. Here, the Ar f substituent effect is mainly steric. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)