Mono- and trichloride clathrochelate iron (II) chloroglyoximates and their functionalization: The effect of the substituents in the clathrochelate framework on the reactivity of the chlorine-containing fragments in nucleophilic substitution reactions

The direct template macrocyclization of the three chloroglyoxime molecules with boron-containing Lewis acids on the iron (II) ion matrix led to the formation of a mixture of fac- and mer-isomers of clathrochelate complexes in the 1:3 ratio, which is equal to a statistical one. The yields of tris-chloroglyoximate precursors (25–40%) were practically the same as those for their earlier-studied chloromethylglyoximate analogs, whereas the reactivity of the former complex has proved to be markedly higher than that of the latter clathrochelates: the triamine clathrochelates were the major products in the reaction of (mer + fac)-Fe(ClHGm)3(BC6H5)2 and (mer + fac)-Fe(ClHGm)3(BF)2 complexes with n-butylamine, whereas for (mer + fac)-Fe(ClCH3Gm)3(BC6H5)2 clathrochelate an analogs reaction produced the diamine complex only. The mixture of the diamine clathrochelate isomers was obtained in both cases with less reactive cyclohexylamine. The reaction of the trichloride precursors with alkyl- and arylthiols in the presence of triethylamine has proceeded more readily and led to the formation of trisulfide clathrochelates.The monochloride FeBd2(ClHGm)(BF)2 complex, obtained by the condensation of the macrocyclic bis-dioximate [FeBd2(BF2)2 (CH3CN)2] with chloroglyoxime, readily underwent the nucleophilic substitution of the reactive chlorine atom with amines and thiol-containing functionalizing agents. The clathrochelate complexes with pendant substituents, containing reactive terminal HO-, H2N- and HS-groups, were obtained. Thiolate FeBd2(H(HSCH2CH2S)Gm)(BF)2 clathrochelate underwent the intramolecular elimination of ethylene sulfide in basic media to yield the clathrochelate with attached HS-group. Clathrochelates obtained have been characterized using elemental analysis, PD and MALDI-TOF mass, IR, UV–Vis, 57Fe Mössbauer and 1H, 13C and 11B NMR spectroscopies, and X-ray crystallography (for the fac-Fe(ClHGm)3(BC6H5)2 and FeBd2{H(CH3S)Gm}(BF)2 · 2C6H6 complexes). X-ray structure of a fac-isomer of clathrochelate complex was solved for the first time in this study. Configurations intermediate between trigonal prismatic and trigonal antiprismatic have been deduced for the low-spin iron (II) ion coordination polyhedra of all clathrochelates obtained using 57Fe Mössbauer parameters.

Graphical abstractThe template reaction of chloroglyoxime with boron-containing Lewis acids on iron (II) afforded the fac- and mer-isomers of trichloride clathrochelates. Their reactions with amines, alkyl- and arylthiolates gave functionalized derivatives. The condensation of [FeBd2(BF2)2(CH3CN)2] with chloroglyoxime resulted in FeBd2(ClHGm)(BF)2 precursor, which produced the clathrochelates with reactive terminal groups by nucleophilic substitution.Figure optionsDownload full-size imageDownload as PowerPoint slide