Facile Synthesis of Bismuth and Antimony Complexes Supported by Silylated Calix[5]arene Ligands

A series of bismuth(III) and antimony(III) complexes supported by silicon-containing calix[5]arene ligands were synthesized and fully characterized by NMR, X-ray, IR, mp, UV/vis, and elemental analysis. Reaction of the para-tert-butylcalix[5]arene [tBuC5(H)5] disodium salt, Na2tBuC5(H)3, with 1 equiv of R2SiCl2 (R = Me, iPr, Ph, CH?CH2) or treatment of the tBuC5(H)5 lower rim monobenzyl ether [tBuC5(Bn)(H)4] in a 1:1 ratio with Me2Si(NMe2)2 yields the tBuC5(SiRR?)(H)3 (1?5) and tBuC5(Bn)(SiMe2)(H)2 (6) ligands, respectively. The 1H NMR spectra of the tBuC5(SiRR?)(H)3 (1?5) ligands show three pairs of doublets and three singlets for the tBu peaks, consistent with a Cs symmetry. In the case of the tBuC5(Bn)(SiMe2)(H)2 (6) ligand, the presence of the monobenzyl group changes the 1H NMR patterns to indicate a C1 symmetry. Treatment of tBuC5(SiRR?)(H)3 (1?5) or tBuC5(Bn)(SiMe2)(H)2 (6) with 1 equiv of M(OtBu)3 (M = Bi, Sb) or Sb(NMe2)2 readily yields metalated products of the type [M{tBuC5(SiRR?)}] (7?16) and [MX{tBuC5(Bn)(SiMe2)}] (X = OtBu, (NMe2)2) (17?19), respectively. All monometallic complexes [M{tBuC5(SiRR?)}] (7?19) display excellent solubility in organic solvents including pentane and hexane. The 1H NMR patterns for complexes 7?16 are consistent with a 1,2- or 1,3-alternate conformation while complexes [MX{tBuC5(Bn)(SiMe2)}] (17?19) display patterns for a C1 symmetry. All crystals show monomeric structures. Ligand tBuC5(SiPh2)(H)3 (3) displays a distorted cone conformation while the presence of the monobenzyl ether in tBuC5(Bn)(SiMe2)(H)2 (6) forces a partial cone conformation. Complexes 7?19 all display a distorted 1,2-alternate conformation with the metal centers displaying coordination numbers of three, four or five. No SiM interactions were observed.