Syntheses, Structures, Bonding and Photoelectron Spectra of "Push-Pull"-Substituted P-[2,6-Bis(trifluoromethyl)phenyl]-?2λ3-iminophosphanes

Article abstract of DOI:10.1002/ejic.200300823

?²λ³-"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 = 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), Ar_fP=NH (2), Ar_fP=NSiMe3 (3), Ar_fP=NtBu (4), HP=NNMe2 (5) and Ar_fP=NNMe2 (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 ?-system of the Ar_f group is almost orthogonal to the ?_P=N system, preventing any stabilizing interaction between the ?_P=N and ?*_b1(aryl) orbitals previously observed for the Ar_fPH^- anion. Here, the Ar_f substituent effect is mainly steric.