First example of perfluoroalkylation of a quasi-aromatic encapsulating ligand: 2,5-Dithiahexane-assisted reaction of the iron(II) diiodoclathrochelate with trifluoromethylcopper(I)

Perfluoroalkylation of an iron(II) diiodoclathrochelate precursor with trifluoromethyltrimethylsilane and copper(I) iodide in THF using 2,5-dithiahexane as a co-ligand and potassium fluoride as the base afforded mono- and bis-trifluoromethylated cage complexes in moderate yields. These complexes were characterized using elemental analysis, MALDI-TOF mass spectrometry, IR, UV–Vis, 1H, 11B, 19F and 13C{1H} NMR spectroscopies, and by X-ray crystallography. The geometry of their FeN6-coordination polyhedra is intermediate between a trigonal prism and a trigonal antiprism, the encapsulated iron(II) ions are located almost in the center of these polyhedra. The average Fe–N distances (av. 1.91 Å), the distortion φ angles (approximately 26°) and the heights h of the coordination polyhedra (2.31 Å) are characteristic of the boron-capped iron(II) clathrochelates. The anodic ranges of the cyclic voltammograms for the trifluoromethylated iron(II) clathrochelates contain one-electron waves of an irreversible oxidation assigned to the metal-centered redox process Fe2 +/3 +, while those in their cathodic ranges were assigned to the Fe2 +/+ reduction. The ribbed functionalization of the iron clathrochelates with trifluoromethyl substituent(s) destabilizes both their oxidized and reduced forms.