| The thesis focused on the study of reactivity of alunminum alkyls Al(alkyl)3(alkyl = Me or Et)with functionalized nitrogen containing heterocycles,leading to the formation of different organoaluminum complexes via different reaction processes.Synthesis,structural characterization,and catalytic activity of these new organoaluminum complexes were also studied.The thesis contains the following parts:1)The reactions of Al Me3 or Al Et3 with 2-imino functionalized pyridyl or 2-imino or 3-imino functionalized indole were respectively studied,leading to the isolation of different organoaluminum complexes via different reaction processes.The reaction of the imino-functionalized pyridine Cy[N=CMe-2-(C5H4N)]2(L1)derived from 1-(pyridin-2-yl)ethanone and trans-1,2-cycloheaxnediamine with Al Et3 gave the aluminum complex Cy[NC(Me)(Et)-2-(C5H4N)Al Et2]2(1),in which the two ketimine groups of the ligand were transformed into the amido functionality through the addition of the ethyl group to C=N bond.The reaction of L1 with Al Me3 afforded the aluminum complex Cy[NC(=CH2)-2-(C5H4N)Al Me2]2(2)via a sp3 C-H activation with elimination of methane.The reaction of 2-imino-functionalized indole(2-(RN=CH)C8H5NH(R = tBu(L2),C6H5(L3),2,6-Me2C6H3(L4))with Al Me3 or Al Et3 afforded only the indole deprotonated complexes [2-(RN=CH)C8H5N]Al Me2(R = tBu(3),C6H5(4),2,6-Me2C6H3(5))and [2-(2,6-Me2C6H3N=CH)C8H5N]Al Et2(6)respectively with similar structures.The reaction of 3-imino-functionalized indoles(3-(RN=CH)C8H5NH(R = tBu(L5),C6H5(L6))with Al Me3 afforded the dimeric complex cis-[(?-?1:?1-3-tBu N=CH)C8H5NAl Me2]2(7)and tetrameric complex [(?-?1:?1-3-C6H5N=CH)C8H5NAl Me2]4(8)respectively.These results suggested that the steric hindrance and electronic effect of heterocyclic compounds affected the reactivity with aluminium alkyl.The structures of complexes 1-8 were determined by spectroscopic methods and confirmed by X-ray crystallographic analysis.These aluminum complexes showed high catalytic activity on the addition of amines to carbodiimides to form guanidines.The mechanism of the catalytic process was studied by control experiments and 1H NMR monitoring,a probable mechanism for the guanylation reaction was proposed with the isolation of reaction intermediate [2-(2,6-Me2C6H3-N=CH)C8H5N][Cy N=C(4-Me C6H3N)(NHCy)]Al Me(9).2)Reactivity of 1-alkyl 2-amino-or 2-imino-functionalized pyrroles with aluminum alkyls was investigated resulting in isolation of a series of aluminum alkyl complexes via different processes.Treatment of 1-Bn-2-imino-functionalized pyrrole 1-Bn-2-(2,6-iPr2C6H3N=CH)C4H3N(L7)with Al Me3 produced only iminocoordinated aluminum complex 1-Bn-2-(2,6-iPr2C6H3N=CH)C4H3NAl Me3(10).While reactions of 1-Bn or Me-2-amino-functionalized pyrroles with aluminum alkyls produced the aluminum alkyl complexes {[?1-?-?1:?1-1-R1-2-(2,6-iPr2C6H3 NCH2)C4H2N]Al R}2(R1 = Bn,R = Me(11);R1 = Bn,R = Et(12);R1 = R = Me(13);R1 = Me,R = Et(14))bearing 3-carbon bonded pyrrolyl ligands via C–H ?-bond metathesis reaction.Further reactions of complexes 11-14 with a stoichiometric amount of isopropyl alcohol(iPr OH)afforded the corresponding aluminum alkoxide complexes [1-R1-2-(2,6-iPr2C6H3NCH2)C4H3N Al R(?-OiPr)]2(R1 = Bn,R = Me(15);R1 = Bn,R = Et(16);R1 = R = Me(17);R1 = Me,R = Et(18))through selectively cleavage of the Al-C(Pyr)bond.The solid state structures of the aluminum complexes 10-15 and 17 were confirmed by an X-ray diffraction study.These aluminum alkyl complexes exhibited notable activity toward the ring-opening polymerization of ?-caprolactone and L-lactide in the absence of alcohol.The end group analysis of ?-CL oligomer gave a strong support that the polymerization proceeded via a coordination-insertion mechanism involving a unique Al-C(Pyr)bond initiation providing pyrrolyl-end functionalized polyesters.3)The bis-imino bridged-bis-indoles R1(N=CHC8H5NH)2(L10-L14)(R1 =-CH2CH2-(L10);-CH2CH2CH2-(L11);-CH2CMe2CH2-(L12);rac-Cy(L13);R,R-Cy(L14),with different backbone linkers were synthesized,and reactivity of these compounds with aluminum alkyls(Al Me3 or Al Et3)was investigated resulting in isolation of a series of new aluminum alkyl complexes R1(N=CHC8H5N)2Al R(19-28)(R1 =-CH2CH2-,R = Me(19);R1 =-CH2CH2-,R = Et(20);R1 =-CH2CH2CH2-,R = Me(21);R1 =-CH2CH2CH2-,R = Et(22);R1 =-CH2CMe2CH2-,R = Me(23);R1 =-CH2CMe2CH2-,R = Me(24);R1 = rac-Cy,R = Me(25);R1 = rac-Cy,R = Et(26);R1 = R,R-Cy,R = Me(27);R1 = R,R-Cy,R = Et(28)bearing N,N,N,N-tetradentate ligands.Complexes 19-28 were characterized by NMR spectroscopy?elemental analysis.The structures of complexes 19?20?22?24?25-28,were determined by X-ray crystallographic study and the crystal structures showed that the lengths of the backbone of the ligands affected the geometric configuration of complexes.The catalytic activities of complexes 19-28 for polymerization of meso-lactide and rac-lactide in the presence of 1 equiv of isopropyl alcohol were investigated.The results showed that all complexes are effective initiators for the polymerization of rac-lactide and meso-lactide,and the molecular weight distribution is narrow.The aluminum complexes having ligands with backbone bearing three carbon atoms exhibited significantly higher catalytic activity than those of aluminum complexes having ligands with backbone bearing two carbon atoms. |
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