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.

A New Series of Cobalt and Iron Clathrochelates with Perfluorinated Ribbed Substituents

“…The CoN 6 -coordination polyhedron in Co((C 6 F 5 ) 2 Gm) 3 (BC 6 F 5 ) 2 ( 6 ) is close to the trigonal prism (TP, Scheme 2; the distortion angle φ = 1.4°), whereas in the other two (φ = 10°–14°), it adopts a geometry that is intermediate between a TP (φ = 0°) and a trigonal antiprism (TAP, φ = 60°). For comparison, the φ value in the iron(II) complex Fe((C 6 F 5 ) 2 Gm) 3 (B n -C 4 H 9 ) 2 ( 1 ) is equal to 25.4°, 6 and the metal ion is almost in the center of a cage framework. The degree of this TAP–TP distortion is affected not only by the nature of the metal ion but also by the nature of the ribbed substituents.…”

“…Electromeric characteristic of halogen atoms resemble those of (per)fluoroaryl groups, 5 so that suitably decorated clathrochelates can show similar electrocatalytic activity but have the stability that is even higher. 6 Indeed, (per)fluorinated iron and cobalt(II) clathrochelates with pendant (per)fluoroarylsulfide substituents are known to withstand harsh acidic conditions. 7 In these complexes, however, the presence of bridging sulfur atoms does not allow the (per)fluoroaryl groups to stabilize the reduced (and probably electrocatalytically active) metal(I)-containing intermediate.…”

Large, heterometallic coordination cages based on ditopic metallo-ligands with 3-pyridyl donor groups

“…The bond lengths and angles found for the trigonal prismatic Fe core of 1 and 2 are within the range observed for other Fe-based clathrochelate complexes. 12 …”

Apically linked iron(ii) α-dioximate and α-oximehydrazonate bis-clathrochelates: synthesis, structure and electrocatalytic properties

“…calc. for C 33 H 54 N 18 O 6 B 4 Fe 2 F 8 (%): C,35.84;H,4.92;N,22.80. Found (%): C,35.94;H,5.01;N,22.77.…”

“…for C 28 H 38 N 6 O 6 B 2 Fe (%): C,53.07;H,6.06;N,13.29;Fe,8.84. Found (%): C,52.97;H,5.91;N,13.09;Fe,8.73. 1 H NMR (CD 2 Cl 2 ): δ, ppm: 0.40 (br.…”