Synthesis and X-ray structure of methyl esters of the dicarboxyphenylsulfide iron(II) clathrochelates

All six constitutional isomers of the dimethoxy-terminated clathrochelate FeBd₂((CH₃OOCC₆H₄S)₂Gm)(BF)₂ (where Bd^2? is α-benzildioxime dianion, Gm is glyoxime residue, and BF is fluoroboron capping group) were obtained under mild reaction conditions by nucleophilic substitution of their dichloroclathrochelate precursor with the corresponding methyl ester of carboxyphenylthiolate anion generated in situ in the presence of triethylamine. In the case of homodifunctionalized cage complexes with equivalent ortho-, meta-, or para-substituted arylsulfide groups, 1.5-fold excess of methyl ester of the corresponding mercaptobenzoic acid was added. In the case of their heterodifunctionalized macrobicyclic analogs, subsequent addition of one equivalent of the first nucleophilic agent and one equivalent of the second nucleophile was used. The complexes were characterized using elemental analysis, MALDI-TOF mass spectrometry, IR, UV–vis, ¹H and ¹³C{¹H} NMR spectra, and by single-crystal X-ray diffraction. In all these molecules, the encapsulated iron(II) is situated in the center of FeN₆-coordination polyhedron, the geometry of which is intermediate between a trigonal prism and a trigonal antiprism with the average distortion angles φ from 24.7 to 25.2°. The absence of strong intermolecular interactions and the substantial sterical clashes hampering a rotation around the single C–S bonds, resulted in different orientations of the functionalizing arylsulfide substituents at a cage framework.