Synthesis and Characterization of Bismuth(III) and Antimony(III) Calixarene Complexes

A series of calixarene bismuth and antimony complexes have been fully characterized by NMR, X-ray, IR, UV/vis, and elemental analysis. The reactions of SbCl3 with the monosodium salt of p-tert-butylcalix[4]arene (ButC4), ButC4·Na, and the tetralithium salt of para-tert-butylcalix[4]arene, ButC4·Li4, afforded two diantimony calix[4]arene complexes ButC4(SbCl)2, with different 1H NMR spectra and different THF coordination, but the same core structures. Other calix[4]arene antimony complexes (HC4(SbCl)2 2 and AC4(SbCl)2 3, diantimony chloride complexes of calix[4]arene and p-allylcalix[4]arene) and calix[4]arene bismuth complexes (ButC4(BiCl2)2Li2 4, HC4(BiCl2)2Li2·6DMSO 5, and AC4(BiCl2)2Li2·4THF 6) were prepared by the reactions of MCl3 (M = Sb or Bi) with RC4·Li4 (R = But, H, or allyl) in a 2:1 molar ratio in THF. The same strategy was applied for ButC8 (p-tert-butylcalix[8]arene), and the desired bismuth complex [ButC8(BiCl2)4(μ-Cl)2Li6][4THF·7DME] 12 was successfully synthesized. Complex 12 contains a planar Bi4 core with four terminal chlorine atoms, which adopt a syn arrangement with respect to the plane defined by four bismuth atoms, and orient away from each other. A calix[4]arene monobismuth complex 11 was prepared by the reaction of Bi(OBut)3 with the 1,2-disubstituted benzyl ether of calix[4]arene. Complexes 1−6 contain central planar M2(μ-O)2 (M = Sb or Bi) four-membered rings, similar to four-membered rings observed in other calix[4]arene main group metal complexes. Intramolecular bismuth-arene π interactions are observed in complexes 4−6 and 11 but not 12.