Perfluoroarylation of Iron(II) Di‐ and Hexaiodoclathrochelates – Synthesis, X‐ray Structure, and Properties of the First Cage Complexes with Inherent Pentafluoro­phen­yl Substituent(s)

Abstract

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 X-ray crystallography. The encapsulated iron(II) ions in the X-rayed 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.