Facile Synthesis of Bismuth(III) and Antimony(III) Complexes Supported by Silylated Calix[5]arenes.

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, Na2·tBuC5(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 Si···M interactions were observed.