Clathrochelates meet phosphorus. New thio- and phosphorylation reactions of an iron(ii) dichloroclathrochelate precursor and preparation of its first phosphorus(iii)-containing macrobicyclic derivative

Abstract

Phosphorylation reactions of an iron(II) dichloroclathrochelate FeBd₂(Cl₂Gm)(BF)₂ (where Bd²⁻ and Cl₂Gm²⁻ are α-benzildioxime and dichloroglyoxime dianions, respectively) with diphenylphosphine oxide and diethyl thiophosphite were performed under phase-transfer conditions. In the case of diethyl thiophosphite as a P-nucleophile, the best yields were obtained in the dichloromethane–50% NaOH aqueous solution–5 mol% triethylbenzylammonium chloride (TEBAC) system. The use of different molar ratios of a macrobicycle precursor and this thiophosphorylating agent allowed us to obtain both the mono- and the diphosphorylated cage complexes. Nucleophilic substitution with diphenylphosphine oxide was performed in the K₂CO₃–acetonitrile–5 mol% TEBAC system, giving only the corresponding monophosphorylated iron(II) complex in high yield even in the presence of an excess of this P-nucleophile. The phosphorus(V)-containing clathrochelate product was reduced with an excess of silicoform to give an iron(II) macrobicycle with an inherent diphenylphosphine group in an almost quantitative yield, which was then characterized by ³¹P{¹H} NMR and single-crystal X-ray diffraction; it easily undergoes re-oxidation to the initial clathrochelate. The synthesized phosphorus(V)-containing cage complexes were characterized using elemental analysis, MALDI-TOF mass, IR, UV-Vis, ¹H, ¹¹B, ¹³C{¹H}, ¹⁹F{¹H} and ³¹P{¹H} NMR spectra, and by single-crystal X-ray diffraction.