Perfluoroarylation of Iron(II) Di- and Hexaiodoclathrochelates – Synthesis, X-ray Structure, and Properties of the First Cage Complexes with Inherent Pentafluorophenyl Substituent(s)статья
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Дата последнего поиска статьи во внешних источниках: 18 марта 2017 г.
Аннотация:Perfluoroarylation of a known iron(II) diiodoclathrochelate
precursor and its new n-butylboron-capped hexaiodomacrobicyclic
analog with pentafluorophenylcopper(I) gave the
first iron(II) cage complexes with inherent perfluoroaryl substituent(
s). The complexes synthesized were characterized
by elemental analysis, MALDI-TOF mass spectrometry, IR,
UV/Vis, 1H, 11B, 19F, and 13C{1H} NMR spectroscopy, and Xray
crystallography. The encapsulated iron(II) ions in the Xrayed
hexaiodo- and di- and hexa(pentafluorophenyl)ated
iron(II) clathrochelates are located almost in the centers of
their FeN6 coordination polyhedra. The geometry of the
hexaiodoclathrochelate precursor is trigonal prismatic (TP,
distortion angle φ = 4.5°), whereas the perfluoroarylated
iron(II) clathrochelates are intermediate between a TP and a
trigonal antiprism (TAP) (φ ≈ 25°). This rotation and expansion
from TP to TAP polyhedra causes horizontal spreading,
and the heights h decrease from 2.40 to 2.33–2.35 Å. Anodic
ranges of the cyclic voltammograms (CVs) for the pentafluorophenylated
iron(II) clathrochelates contain one-electron
waves of the metal-centered Fe2+/3+ oxidation, which are
quasireversible in the cyclic voltammetry (CV) timescale.
The potentials for the mono- and difunctionalized clathrochelates
are only slightly different, as a result of steric hindrance
between two pentafluorophenyl substituents in the
same chelate ribbed fragment decreasing their conjugation
with the polyazomethine clathrochelate framework and lowering
the electronic effects. The cathodic ranges of these CVs
contain irreversible waves for encapsulated metal-centered
Fe2+/+ reduction to anionic forms of the cage complexes that
are unstable on the CV timescale.