Characterization of three members of the electron-transfer series [Fe(pda)2]n (n = 2-, 1-, 0) by spectroscopy and density functional theoretical calculations [pda = redox non-innocent derivatives of N,N'-bis(pentafluorophenyl)-o-phenylenediamide(2-, 1?, 0

[摘要]：The four-coordinate Fe complexes, [FeIII(pda2-)(pda?)] (1) and [AsPh4]2[FeII(pda2-)2] (2) were synthesized and fully characterized; pda2- is the closed-shell ligand N,N'-bis(pentafluorophenyl)-o-phenylenediamido-(2-), and pda? represents its 1-electron-oxidized p-radical anion. Single-crystal x-ray diffraction studies of 1 and 2 performed at 100(2) K reveal a distorted tetrahedral coordination environment at the Fe centers, as a result of the intramol. p-p interactions between C6F5 rings. The electronic structures of 1 and 2 were unambiguously detd. by a combination of 57Fe Mossbauer and electronic spectroscopy, magnetic susceptibility measurements, x-ray crystallog., and DFT calcns. Compd. 1 contains an intermediate-spin FeIII ion (SFe = 3/2) strongly antiferromagnetically coupled to a p-ligand radical (SR = 1/2) yielding an St = 1 ground state. Complex 2 possesses a high-spin FeII center (SFe = 2) with two closed-shell dianionic ligands. Complexes 1 and 2 are members of the redox series [Fe(pda)2]n with n = 0 for 1 and n = 2- for 2. The anion n = 1- is reported previously in the coordination salt [Fe(dad)3][Fe(pda)2] (3; dad = N,N'-bis(phenyl)-2,3-dimethyl-1,4-diaza-1,3-butadiene). A complicated temp.-dependent electronic structure was obsd. for this salt. Here, DFT calcns. performed on 3 confirm the previous constitutes an electron-transfer series, which also was established by cyclic voltammetry; the mono- and dications (n = 1+ and 2+) are also accessible in soln., but were not further studied. The 57Fe Mossbauer spectra of [Fe(pda)2]n species in 1 and 3 show extremely large quadrupole splitting consts. due to addn. of the valence and covalence contributions that were confirmed by DFT calcns.

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