Study On Polymerization Of ε-caprolactone By Rare Earth Thiolate Complexes

In this paper, a series of rare earth thiolate complexes were designed and synthesized.Their catalytic performances for the polymerization of-caprolactone were studied inorder to develop a kind of catalyst being active and having living/controlled character.(1) Polymerization of-caprolactone catalyzed by two biscomponent catalysts ofCp3Ln/HOCH2CH2NMe2and Cp3Ln/HSCH2CH2NMe2(Ln=Sm, Yb) was studied andcompared with those by single component catalysts of Cp3Ln (Ln=Sm, Yb). The catalyticactivity decreased in the order of Cp3Yb/HOCH2CH2NMe2> Cp3Sm/HOCH2CH2NMe2>Cp3Yb/HSCH2CH2NMe2> Cp3Sm/HSCH2CH2NMe2> Cp3Sm> Cp3Yb. The addition ofmercaptan improved the catalytic activity of Cp3Ln, because Cp3Ln can react withHSCH2CH2NMe2to form corresponding lanthanocene thiolates via a reversibleequilibrium reaction. Because the equilibrium constant is so small, the effect of addition ofmercaptan for Cp3Sm is rather limited. The reaction of Cp3Ln and HOCH2CH2NMe2cancompletely afford the corresponding lanthanocene alkoxides. The crystal structure of[Cp2Sm(-OCH2CH2NMe2)]2was determined.(2) Reaction of LnCl3with3equivalent of CpNa in THF first, and then with1equivalent of HSCH2Ph, led to complexes of [Cp2LnSCH2Ph]2(Ln=Sm, Yb). The crystalstructure of [Cp2YbSCH2Ph]2was determined by X-ray diffraction analysis.(3) The catalytic behavior for the polymerization of-caprolactone by lanthanidethiolate complexes of [Cp2LnSCH2Ph]2and Cp2Ln(SC6H4-p-CH3)(Ln=Sm, Yb) wasstudied. It was found that [Cp2YbSCH2Ph]2has the best catalytic activity. As the catalystdosage is1/500(mol) of monomer, and the polymerization proceeded at35℃, there isliving/controlled sign for [Cp2YbSCH2Ph]2.(4) Complexes of LLnCp(THF)2(L2-=Me2NCH2CH2CH2N{CH2-(3,5-tBu2-C6H2-2-O-)}2; Ln=Sm, Er, Yb) and [LLnSCH2Ph(THF)]2(Ln=Sm, Yb) weresynthesized and characterized by infrared spectra, elemental analyses and X-raycrystallography.(5) Polymerization of-caprolactone catalyzed by [LLnSCH2Ph(THF)]2(Ln=Sm, Yb)was studied. The catalytic activity decreased in the order of Yb>Sm. The polymerizationprocess by [LYbSCH2Ph(THF)]2shows living/controlled character.