Synthesis, Characterization And Application Of New Organobismuth Compounds Bearing Tridenate Ligands

Bismuth, which has an external orbits electronic configuration of 4f145d106s26p3, is a nontoxic and noncarcinogenic element. Many Bi compounds are low in toxicity and can be safely used in many areas such as medicine, catalysis, and organic synthesis. In the past thirty years, as an important branch of bismuth chemistry, organobismuth chemistry had been widely developed. Up to now, the development of organobismuth chemistry has suffered from several shortcomings:(1) poor stability of Bi-C bonds in many organobismuth compounds, (2) only little fraction of the reported organic ligands are suitable for constructing organobismuth compounds, and (3) the functionalities of them have not been disclosed. From the standpoint of "Green Chemistry" and "Sustainable Development", it is envisaged that Bi compounds will find new scientific value and applications.Based on the character of external electronic configuration of Bi and the development of organobismuth chemistry,11 tridentate organic ligands bearing O, S or N atoms as coordination atoms and 30 new air-stable organobismuth compouds were synthesized. The structure and properties of the compounds were characterized by NMR, FT-IR, X-Ray single crystal diffraction, TG-DSC techniques, etc. Moreover, their potential applications in antiproliferative activity on cancer cell, CO2 fixation and Lewis acid catalyzed C-C bond forming reactions were investigated. Some innovative results and conclusions were obtained as follows.(1) Synthesis of ligand precursors:9 ligand precursors bearing N, O or S coordinating atoms and 2 asymmetric ligand precursors containing N or O coordinating atoms were synthesized in high yield and selectivity using 1-Br-2-CH3-C6H4 and 1-Br-2-CH3-C10H6 and NBS as starting raw material in the presence of K2CO3 or amine as neutralizing agent.(2) Eight organobismuth chlorides [S(C6H4CH2)2BiCl,tBuN(C6H4CH2)2BiCl, C6H5N(C6H4CH2)2BiCl, C6H11N(C6H4CH2)2BiCl et al.] were synthesized from the tridentate ligand precursors [(2-BrC6H4CH2)2S, (2-BrC6H4CH2)2NR(R=tBu, C6H5, C6H11) et al]. Three cyclic hypervalent organobismuth compounds bearing physiological activity organogermanium segment [S(CH2C6H4)2BiO2C(CH2)2GePh3, C6H5N(C6H4CH2)2BiO2C(CH2)2GePh3 and C6H11N(C6H4CH2)2Bi02C(CH2)2GePh3] were synthesized by the reaction of the organobismuth chlorides withβ-(triphenyl-germyl)-propionic acid in the presence of NaOH. Single crystal X-ray diffraction analysis results reveal that the Bi-S or Bi-N bond lengths in thiabismocine or azabismocine derivatives are dependent on the substituted groups which are acting on the N and Bi atom. The replacement of Cl atom by organogermanium segment leads to the lengthening of the Bi-S or Bi-N bonds. The six compounds show antiproliferative activities on MGC-803, better than that of cisplatin; and the IC50 value for compound S(CH2C6H4)2BiO2CCH2CH2GePh3 is 0.7μM. It is apparent that a proper coordination ability of Bi3+ and the introduction of organogermanium group are beneficial for achieving good antiproliferative activitves.(3) Eight cyclic hypervalent organobismuth compounds{S(C6H4CH2)2BiOH, RN(C6H4CH2)2BiOH(R=tBu, C6H5 and C6H11); [S(C6H4CH2)2Bi]2O, [RN(C6H4CH2)2-Bi]2O (R=tBu, C6H5 and C6H11)} were synthesized from the organobismuth chlorides [S(C6H4CH2)2BiCl, RN(C6H4CH2)2BiCl(R=tBu, C6H5 and C6H11)] bearing S, N coordination atoms. Four organobismuth carbonates{[S(C6H4CH2)2Bi]2CO3, [RN(C6H4CH2)2Bi]2CO3(R=tBu, C6H5 and C6H11)} were obtained through the reaction of CO2 with the organobismth oxides or hydroxides respectively. It was found that hydroxide, oxide and carbonate of organobismuth compounds can be mutually transformed under appropriate conditions. The results of adsorption/regeneration experiments indicated that these oxides showed high efficiency for the capture of carbon dioxide under relatively mild conditions. Compared with amine, this absorbent has the advantages such as high absorption capacity of carbon dioxide, no corrosion, low energy consumption and regeneration temperature. Therefore, it will find potential application in CO2 capture.(4) Cationic organobismuth complex [tBuN(CH2C6H4)2Bi]+[B(C6F5)4]- was the first time used to examine for the coupling of CO2 into cyclic carbonates, using terminal epoxides as substrates and tetrabutylammonium halide as co-catalyst in a solvent-free environment under mild conditions. It was shown that both of epoxide conversion and cyclic carbonate selectivity (near 100%) are high. The catalyst can be easily separated and reused with little decline in activity and selectivity. A plausible mechanism for the coupling reaction over [tBuN(CH2C6H4)2Bi]+[B(C6F5)4]-+Bu4NI has been proposed. The excellent catalytic performance is possibly related to proper Lewis acidity of the cationic organobismuth complex.(5) Eleven new hypervalent organobismuth(Ⅲ) compounds 79～89 RN(C6H4-CH2)2BiX(R=tBu, C6H5 and C6H11; X=BF4, OSO2CF3, OSO2C4F9 and OSO2C8F17) with strong Lewis acidity, were synthesized by the reaction of organobismuth chlorides RN(C6H4CH2)2BiCl(R=tBu, C6H5 and C6H11) with silver perfluorooctane -sulfonate and silver tetrafluorborate, respectively. C6H11N(CH2C6H4)2BiBF4 and C6H11N(C6H4CH2)2Bi(OSO2C8F17) were examined as catalysts for C-C bond forming reactions. It was found that 86 shows good catalytic efficiency in the allylation reaction with tetraallyltin in a medium of aqueous methanol (CH3OH/H2O=9:1), and 89 exhibits high catalytic efficiency towards one-pot Mannich-type reaction of ketones with aromatic aldehydes and aromatic amines in water. Furthermore, these two catalysts show good stability and recyclability, and is almost independed of the reactant substrates.