Synthesis And Applications Of Air-stable Organoantimony Complexes Catalysts

Antimony resources are very rich in China, and organoantimony compounds have wide applications in organic synthesis, materials science and living systems as their various functions. However, compared with transition metals and rare earth metals, the research on organoantimony complexes is relatively rare, especially its catalytic activity. This phenomenon may mainly due to the weakness of the Sb-C bond, those organoantimony complexes are very unstable under air atmosphere. In addition, due to the weak acid strength and low catalytic activity, applications of these complexes as Lewis acids are very limited. Furthermore, researches about the relationship between the molecular structure of the organic antimony compounds and their activity are very few. Thus, developing a series of high catalytic activity, air-stable organoantimony compounds and explain the relationship between the molecular structure of the organic antimony compounds and their catalytic activity is of particular importance and highly desired in organoantimony chemistry.Base on the 5,6,7,12-tetrahydrodibenzo[c,f][1,5]azastibocine framework, a series of organoantimony complexes 4-10 were synthesized as expected. The component, structure and physicochemical properties of those compounds were characterized by nuclear magnetic resonance (NMR), elemental analysis, and single crystal X-ray analysis, etc. The relationship between the molecular structure of the organic antimony compounds and their catalytic activities were also tested. Some special ligands were also reported in this paper. The results are summarized as follows:(1) Based on the 5,6,7,12-tetrahydrodibenzo[c,f][1.5]azastibocine framework, a series of organoantimony complexes RN(C6H4CH2)2SbCl (R=’Bu(4),c-C6H11(5). Ph(6)) and PhN(C6H4CH2)2SbX(X=Br(7),1(8)F(9).BF4-(10)) were synthesized by slightly modulate the organic groups connected to the nitrogen and the halogen bonded to the antimony. We found that the strength of the N→Sb coordination bond would be influenced by the electron withdrawing ability of the organic groups connected to the nitrogen and the halogen bonded to the antimony.(2) Mannich reaction was adopted to test the catalytic applications of organoantimony complexes 4-9. The results represent the theory of the the catalytic ability would be influenced by the strength of the N→Sb coordination bond. We found that the complex 9 show the optimal catalytic activity. The catalyst also shows good activity for the synthesis of (E)-α,β-unsaturated ketones by a condensation reaction between aldehydes and cyclohexanone in the presence of propylamine. In addition, it exhibits good stability and recyclability with good potential application.(3) Base on the special function and biological activity of carbazole, Ligand precursors 3,6-Di-tert-butyl-carbazole(16),3,6-di-tert-butyl-1,8-diiodo-carbazole (17), 3,6-bis(1,1-dimethylethyl)-1,8-di-2-thienyl-Carbazole (18) were synthesized in high yields using carbazole as starting materials. And we investigated the optimization of reaction conditions. Carbazole ligands may increase the activity of organoantimony complexes, which will find important scientific significance and potential applications.