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 SbCl(3) with the monosodium salt of p-tert-butylcalix[4]arene (Bu(t)C4), Bu(t)C4.Na, and the tetralithium salt of para-tert-butylcalix[4]arene, Bu(t)C4.Li(4), afforded two diantimony calix[4]arene complexes Bu(t)C4(SbCl)(2), with different (1)H 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 (Bu(t)C4(BiCl(2))(2)Li(2) 4, HC4(BiCl(2))(2)Li(2).6DMSO 5, and AC4(BiCl(2))(2)Li(2).4THF 6) were prepared by the reactions of MCl(3) (M = Sb or Bi) with RC4.Li(4) (R = Bu(t), H, or allyl) in a 2:1 molar ratio in THF. The same strategy was applied for Bu(t)C8 (p-tert-butylcalix[8]arene), and the desired bismuth complex [Bu(t)C8(BiCl(2))(4)(mu-Cl)(2)Li(6)][4THF.7DME] 12 was successfully synthesized. Complex 12 contains a planar Bi(4) 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(OBu(t))(3) with the 1,2-disubstituted benzyl ether of calix[4]arene. Complexes 1-6 contain central planar M(2)(mu-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 pi interactions are observed in complexes 4-6 and 11 but not 12.