Synthesis, structural characterization, and reactivity of (thiolato)bismuth complexes as potential water-tolerant Lewis acid catalysts

We have synthesized bismuth complexes incorporating polydentate mono-and di-thiolate ligands and examined their utility as water-tolerant Lewis acid catalysts. The reaction of Bi(OAc)(3) or Bi(NO3)center dot 5H(2)O and the corresponding mono-or di-thiol(ate) yielded the compounds [(SNNS) Bi(OAc)] (4), [(SNNSPr) Bi(OAc)] (5), [(NNS2) Bi(OAc)] (6), [(ONS2) Bi(OAc)] (7), [(ONS2) Bi(NO3)] (8), and [(NNS)(2)Bi][NO3] (9) [H-2(SNNS) = N, N'-dimethyl-N, N'-bis(2-mercaptoethyl) ethylenediamine; H2(SNNSPr) = N, N'-diethyl-N, N'-bis(2-mercaptoethyl) propanediamine; H-2(NNS2) = N, N-diethyl-N', N'-bis(2-mercaptoethyl) ethanediamine; H-2(ONS2) = 2-methoxyethyl-bis(2-mercaptoethyl) amine; H(NNS) = N, N-diethyl-N'-(2-mercaptoethyl) ethanediamine]. The solid-state structures of 4-8 show similar distorted pentagonal pyramidal geometries at the bismuth centre with a thiolate sulfur atom in the axial site, whereas 8 shows second structural arrangement with a distorted trigonal bipyramidal geometry at bismuth. The cation of 9 shows two NNS-bonded ligands and a distorted octahedral geometry at bismuth. Two-dimensional NMR studies of 4-8 show geminal H-1 coupling in-SCH2CH2N-groups and suggests strong dative Bi-N intramolecular interactions. Bi(NO3)(3)center dot 5H(2)O and BiCl3 show high activity toward the esterification of stearic acid, Bi(NO3)(3)center dot 5H(2)O, and 4-7 and 9 show high activity toward the transesterification of methyl stearate in butanol, and 7 shows moderate activity as a catalyst for the transesterification of glyceryl trioctanoate in methanol.