Multistep synthesis, reactivity and X-ray structure of the anisole-terminated iron(II) polyhalogenoclathrochelates and their monoribbed-functionalized macrobicyclic derivatives

• Published in: Transition metal chemistry (Weinheim) Vol. 47; no. 7-8; pp. 321 - 331
• Main Authors: Limarev, Ilya P., Zelinskii, Genrikh E., Mosov, Danila O., Vologzhanina, Anna V., Dorovatovskii, Pavel V., Lazarenko, Vladimir A., Lebed, Ekaterina G., Voloshin, Yan Z.
• Format: Journal Article
• Language: English
• Published: Cham Springer International Publishing 01.12.2022; Springer Nature B.V
• Subjects: Angles (geometry); Anisole; Cages; Catalysis; Chelation; Chemical analysis; Chemistry; Chemistry and Materials Science; Crosslinking; Crystals; Electron spin; Inorganic Chemistry; Iron; Mass spectrometry; NMR; Nuclear magnetic resonance; Nucleophiles; Organometallic Chemistry; Physical Chemistry; Precursors; Single crystals; Substitution reactions; Biorelevant groups; Macrocyclic compounds; Clathrochelates; X-ray diffraction; Halogen bonds; Target delivery; Cage complexes; Ligand reactivity
• ISSN: 0340-4285; 1572-901X
• DOI: 10.1007/s11243-022-00515-6

Multistep synthetic pathway towards a series of the anisoleboron-capped ribbed-functionalized iron(II) cage complexes was developed. Their hexachloroclathrochelate precursor was obtained by the template condensation of three dichloroglyoximate chelating ligand synthons with two molecules of 4-methoxyphenylboronic acid as a Lewis-acidic cross-linking agent on the iron(II) ion as a matrix. It easily underwent a stepwise nucleophilic substitution with S 2 - and O 2 -dinucleophilic aliphatic (ethanedithiolate) or aromatic (pyrocatecholate) agents, forming the stable X 2 ( X  =  S or O )-six-membered ribbed substituent(s) at a quasiaromatic cage framework. Performing these reactions under the different reaction conditions ( i.e. , at various hexachloroclathrochelate-to-nucleophile molar ratios, a wide range of temperatures and a series of the solvents) allowed to control a predominant formation of its mono-, di- or triribbed-substituted macrobicyclic derivatives. Thus obtained iron(II) di- and tetrachloroclathrochelates can undergo their post-synthetic transformations with active nucleophilic agents. The latter complexes underwent a further nucleophilic substitution with the anionic derivative of n -butanthiol, thus giving the hexasulfide macrobicyclic compound with two functionalizing n -alkyl substituents in one of its three chelate α -dioximate fragments and two apical biorelevant anisole substituents. The obtained iron(II) clathrochelates, possessing a low-spin electronic d 6 configuration, were characterized using elemental analysis, MALDI-TOF mass spectrometry, UV–Vis, 1 H and 13 C{ 1 H} NMR spectroscopies, and by the single-crystal X-ray diffraction experiments for the hexachloroclathrochelate precursor, its dichlorotetrasulfide macrobicyclic derivative and the monoribbed-functionalized hexasulfide cage complex. In all their molecules, the encapsulated iron(II) ion is situated in the centre of its FeN 6 -coordination polyhedron, the geometry of which is intermediate between a trigonal prism and a trigonal antiprism with the distortion angles φ from 21.4 to 23.4°. Halogen bonding between the polyhalogenoclathrochelate molecules in their crystals is observed. Graphical abstract