Synthesis and structure of the first clathrochelate iron(ii) tris-dioximates with inherent nitrile substituent(s) and new dehalogenation – reduction reaction at a quasi-aromatic macrobicyclic framework

Abstract

Monoribbed-substituted mono- and dicyano-functionalized iron(II) macrobicycles were obtained for the first time by the reaction of iron(II) diiodoclathrochelate precursor with copper(I) cyanide-triphenylphosphine complex under mild conditions. The target dinitrile clathrochelate is a minor product of this reaction, whereas the major product contains only one cyano group. The clathrochelates obtained were characterized using elemental analysis, (1)H and (13)C{(1)H} NMR, IR and UV-vis spectroscopy, MALDI-TOF spectrometry and X-ray diffraction crystallography. The geometry of their FeN(6)-coordination polyhedra is intermediate between a trigonal prism (TP) and a trigonal antiprism (TAP); the distortion angles, φ, are 22.6-24.7°. In the molecule of the precursor, the Fe-N distances are close, whereas in the mononitrile macrobicycles those for their functionalized chelate fragments are substantially smaller than the corresponding distances in the α-benzyldioximate moieties. The heights, h, of the TP-TAP coordination polyhedra and the average bite angles, α, (2.33 Å and 39°, respectively) are the same for the X-rayed clathrochelates. The UV-vis spectra indicate a dramatic redistribution of the electron density in the π-conjugated clathrochelate framework caused by functionalization with inherent nitrile substituents. The proposed mechanism of the dehalogenation-reduction reaction of iron(II) diiodoclathrochelate resulting in substitution of their iodine atoms by a cyano group and hydrogen atom includes the anion-radical hydrodehalogenation of this precursor with acetonitrile as a source of hydrogen atom. Then, the monomethinemonoiodine macrobicyclic product underwent a substitution with a cyano group only. The copper(I) cyanide-triphenylphosphine-acetonitrile system is proposed as a tool for the synthesis of nitrile derivatives of electron-withdrawing heterocycles starting from their halogen-containing precursors.

Preparation and characterization of novel [Fe(methylisopropylglyoximato)2(amine)2] mixed chelates

“…the ligand's electronic nature (donicity) and steric hindrance. The azomethine ligand can either be an aliphatic, aromatic, heterocyclic dioxime or a Schiff-base [1][2][3]. Chugaev reported first [4,5] the readiness of Fe II to form complexes with azomethines.…”

“…For the preparation of [Fe(bis-azomethine) 2 (amine) 2 ] types of complexes efficient methods are published in the literature [1][2][3][4][5][6][7][8][9][10]. The synthesis is influenced by different factors e.g.…”

Perfluoroarylation of Iron(II) Di‐ and Hexaiodoclathrochelates – Synthesis, X‐ray Structure, and Properties of the First Cage Complexes with Inherent Pentafluoro­phen­yl Substituent(s)

“…Diiodoglyoxime (denoted as I 2 GmH 2 ) was obtained by a known procedure 11. Diiodoclathrochelate precursor [FeBd 2 (I 2 Gm)(BF) 2 ] was synthesized as described in ref 12. Pentafluorophenylcopper(I) was prepared as described elsewhere 13.…”

The molecular design of cage metal complexes for biological applications: pathways of the synthesis, and X-ray structures of a series of newN2-,S2- andO2-alicyclic iron(ii) di- and tetrachloroclathrochelates

“…The bis-abenzildioximate mono-and dihalogenoclathrochelates of this type have been recognized as the most suitable reactive macrobicyclic precursors of the above biological effectors: they easily undergo well-known classical organic reactions, such as N,O,S,C,Pnucleophilic substitution 12,13,[17][18][19][20][21][22] (including cadmium-promoted reactions with low-active nucleophiles 21,22 ), free-radical substitution, [23][24][25][26][27][28] copper-promoted cyanation, 29 electrophilic addition (for their amine derivatives 30,31 ), and copper(0)-and copper(I)-promoted reactions of halogen exchange, 32 reductive homocoupling, 6,33 and hydrodehalogenation. 29,33 However, the apical functionalization of these fluoroboron-capped halogenoclathrochelate precursors, allowing tuning the physical properties of their macrobicyclic derivatives (in particular their solubility in water or biological media), and performing their efficient binding to a given biological target, is hardly possible (or even impossible). In this work, we aimed to elaborate the efficient synthetic strategies and procedures for a gram-scale synthesis of new iron(II) di-and tetrahalogenoclathrochelates as suitable macrobicyclic precursors for the molecular design of cage metal complexes (prospective biological effectors) and to study their structure and reactivity.…”