Studies On Synthesis, Characterization, Catalytic Properties Of Novel Aluminium, Zinc And Chromium Complexes

In this work 18 metal complexes such as Al, Zn, Cr were synthesized and characterized by 1H and 13C NMR spectroscopy and elemental analyses, as well as X-ray diffraction analysis. The ring opening polymerization of caprolactone initiated by Al, Zn complexes was investigated. The ethylene polymerization initiated by Cr complexes was studied.N, N ligands [ortho-C₆H₄(NMe₂)CH₂NHAr (Ar = 2,6-iPr2C₆H₃, 2a; Ar = 2,6-Et2C₆H₃, 2b; Ar = 2,6-Me₂C₆H₃, 2c; Ar = 4-MeC₆H₄, 2d; Ar = Ph, 2e)] were synthesized from the starting material N,N-dimethylaniline. Treatment of the ligands 2a–e with 1 equiv. of AlMe3 yields Al complexes ortho-(ArNCH₂) C₆H₄NMe₂AlMe₂ (Ar = 2,6-iPr2C₆H₃, 3a; 2,6-Et2C₆H₃, 3b; 2,6-Me₂C₆H₃, 3c; 4-MeC₆H₄, 3d; Ph, 3e) in toluene by alkane elimination reaction. Reaction of ligands 2d, 2e with two equiv. of AlMe3 gets the binuclear Al complexes (Me3Al)[ortho-C₆H₄(NMe₂)- CH₂ArN-μ2]AlMe₂ (Ar = 4-MeC₆H₄, 4d, Ar = Ph, 4e). The new complexes were characterized by 1H and 13C NMR spectroscopy and elemental analyses, and the molecular structures of 3c, 3e and 4e were determined by X-ray diffraction analysis. The Al complexes are efficient catalysts for ring-opening polymerization ofε-caprolactone in the presence of benzyl alcohol in a living fashion yielding polymers with narrow polydispersity values. In order to study the mechanism of polymerization, the active site complex 5 was separated and characterized.N, O ligands (2-dimethylaminophenyl)alcohols [1-HOCPh2-2-NMe₂ C₆H₄ (1a), 1-HOCHPh-2-NMe₂C₆H₄(1b), 1-HOCH(2-F-Ph)-2-NMe₂C₆H₄ (1c)] were synthesized from the starting material N, N-dimethylaniline. Treatment of the ligands 1a–1c with 1 equiv. of AlMe3 yields Al complexes [AlMe₂OCPh2-2-NMe₂C₆H₄ (2a), AlMe₂OCHPh-2- NMe₂C₆H₄ (2b), AlMe₂O-CH(2-F-Ph)-2- NMe₂C₆H₄ (2c)] in toluene by alkane elimination reaction. Reaction of ligands 1b, 1c with two equiv. of AlMe3 gets the binuclear Al complexes (Me₃Al)AlMe₂OCHPh-2-NMe₂C₆H₄ 4b), (Me3Al) AlMe₂OCH-(2-F-Ph)-2- NMe₂C₆H₄ 4c)]. 1b-1c react with ZnEt2 in toluene to get the Zn complexes [ZnEtOCHPh-2-NMe₂C₆H₄ (3b), ZnEtOCH(2-F-Ph)-2-NMe₂C₆H₄ (3c)]. The new complexes were characterized by 1H and 13C NMR spectroscopy and elemental analyses, and the molecular structures of 2a, 4b, 4c and 3b were determined by X-ray diffraction analysis. The Al complexes are efficient catalysts for ring-opening polymerization ofε-caprolactone in the presence of benzyl alcohol in a living fashion yielding polymers with narrow polydispersity values. The Zn complexes 3b-3c are efficient catalysts for ring-opening polymerization of LA in the presence of benzyl alcohol in a controlled manner.Reaction of the lithium salt of 1a-1c with CrCl3(THF)3 in THF gives the four-coordinated Cr(III) complexes (L1)2CrCl, (L2)2CrCl, (L3)2CrCl. Molecular structure of the (L1)2CrCl complex was determined by X-ray crystallography. Upon activation with AlMe3 as cocatalysts, the ethylene polymerization intiated by the Cr(III) complex was investigated.