Synthesis and structural analysis of calix[4]arene-supported iron(III) complexes

The paper describes the reactivity of calix[4]arene dialkyl- or -silylethers H2R2calix, R=Me (1), Bz (2), or SiMe3 (3) (p-tert.butyl-calix[4]arene=H4calix), towards the iron(III) complex [FeCl(NSiMe3)2(thf)] 4. Bis(silylation) of H4calix was achieved using a mixture of NEt3 and Me3SiCl as silylating agent, which is probably the most convenient and cheapest way for the preparation of H2(Me3Si)2calix 3. [FeCl(N{SiMe3}2)2(thf)] 4 has been obtained from the reaction of [FeCl3] and commercially available K[N(SiMe3)2] in THF. The reactions of 4 with H2Me2calix and H2Bz2calix afford mononuclear iron(III) chloro compounds [FeCl(R2calix)] 5 (R=Me) and 6 (R=Bz). The usage of calix[4]arene silyl ether 3 leads to a dinuclear complex [Fe2({Me3Si}calix)2] 7, presumably under Me3SiCl cleavage of a mononuclear calixarene iron(III) chloro complex. The calix[4]arene ether stabilized iron(III) chloro complexes are susceptible to nucleophilic substitution reactions, as exemplified by the reaction of 5 with sodium azide yielding an azido complex [Fe(N3)(Me2calix)] 8. The molecular structures of 4, 5, 6, 7, and 8 in the solid state have been determined by X-ray diffraction.