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

The paper describes the reactivity of calix[4]arene dialkyl- or -silylethers H(2)R(2)calix, R = Me (1), Bz (2), or SiMe3 (3) (p-tert.butylcalix[4]arene = H(4)calix), towards the iron(111) complex [FeCl(NSiMe3)(2)(thf)] 4. Bis(silylation) of H(4)calix 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 H-2(Me3Si)(2)calix 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 H(2)Me(2)calix and H(2)Bz(2)calix afford mononuclear iron(111) chloro compounds [FeCl(R(2)calix)] 5 (R = Me) and 6 (R = Bz). The usage of calix[4]arene silyl ether 3 leads to a dinuclear complex [Fe-2({Me3Si}calix)(2)] 7, presumably under Me3SiCl cleavage of a mononuclear calixarene iron(111) 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(N-3)(Me(2)calix)] 8. The molecular structures of 4, 5, 6, 7, and 8 in the solid state have been determined by X-ray diffraction. (C) 2003 Elsevier B.V. All rights reserved.