Synthesis,Structure And Catalytic Activity Of Rare-earth Metal Bisamido Complexes Incorporating Heterocyclic Tridentate Ligands

This thesis focused on the synthesis,structure and catalytic reactivity of rare-earth metal bisamido complexes incorporating heterocyclic tridentate ligands.The contents consists of two parts:1.synthesis,structure of CNC-pincer rare-earth metal bisamido complexes incorporating diarylamido bridged bis(NHC)(NHC = N-heterocyclic carbene)ligands,and their catalytic reactivity for the addition of terminal alkynes to carbodiimides,and the addition of the P-H bond of phosphines to heterocumulenes;2.synthesis,structure of rare-earth metal bisamido complexes incorporating an NNO type tridentate ligand,and their catalytic activity for polymerization of isoprene.1.Synthesis and catalytic reactivity of CNC-pincer rare-earth metal bisamido complexes incorporating a diarylamido bridged bis(benzyl NHC)ligand for the addition of terminal alkynes to carbodiimidesReaction of a THF suspension of bis[2-(3-benzylimidazolium)-4-methylphenyl]amine dichlorides(H3L1Cl2)with 1 equiv[(Me3Si)2N]3RE(?-Cl)Li(THF)3(RE = Yb,Eu,Sm)in THF at room temperature afforded the only unexpected fused-heterocyclic compound 8,9-dibenzyl-3,14-dimethyl-8a,9-dihydro-8H-benzo[4,5]imidazo[2',1':2,3]imidazo[1,2-a]imidazo[2,1-c]quinoxaline(1)containing imidazolyl-ring and piperidyl-ring which formed through carbene C-C and C-N coupling.However,the reaction of H3L1C12 with 1 equiv[(Me3Si)2N]3Er(?-Cl)Li(THF)3 in toluene at room temperature afforded a CNC-pincer erbium bisamido complex incorporating the diarylamido bridged bis(benzyl NHC)ligand L1Er[N(SiMe3)2]2(2)(L1 =[4-CH3-2-{(C6H4CH2-[N(CH)2CN]} C6H3]2N)in low yield and the above fused-heterocyclic compound 1.The stepwise reaction of H3L1Cl2 with 2 equiv strong bases(n-BuLi or LiCH2SiMe3)in THF for 4 h at-30 ?,followed by treatment with[(Me3Si)2N]3RE(?-Cl)Li(THF)3,generated zwitterion complexes[L12RE][RECl{N(SiMe3)2}3](RE = Y(3),Er(4),Yb(5))together with the fused-heterocyclic compound 1.Additionally,the stepwise reaction of H3L1Cl2 with 6 equiv of NaN(SiMe3)2 in THF for 4 h at-78 ?,followed by treatment with 0.5 equiv YbCl3,generated a novel discrete complex[L12Yb][{Na(?-N(SiMe3)2)}5(?5-Cl)](6).No fused-heterocyclic compound 1 was observed,probably for the reason that low temperature reaction might prevent the carbene carbon from coupling.The one-pot reaction of H3L1C12 with 2 equiv n-BuLi,followed by reaction with[(Me3Si)2N]3RE(?-Cl)Li(THF)3 in THF at-78 ?,generated the CNC-pincer rare-earth metal bisamido complexes incorporating the diarylamido bridged bis(benzyl NHC)ligand L1RE[N(SiMe3)2]2(RE = Er(2),Y(7),Sm(8),Eu(9)).Complexes 2,7-8 could also be prepared by the one-pot reaction of bis(imidazolium)salt(H3L1Cl2)with 5 equiv of NaN(SiMe3)2,followed by treatment with RECl3 in good yields at-78 ?.Complexes 2,7-8 as catalysts for the addition of terminal alkynes to carbodiimides were investigated.Results showed that all complexes exhibited a high catalytic activity towards the addition of terminal alkynes to carbodiimides producing propiolamidines at room temperature.2.Synthesis and catalytic reactivity of the CNC-pincer rare-earth metal bisamido complexes incorporating diarylamido bridged bis(methyl or isopropyl NHC)ligands for the addition of the P-H bond of phosphines to heterocumulenesThe one-pot reactions of bis[2-(3-methylimidazolium)-4-methylphenyl]amine diiodides(H3L3I2)with 5 equiv of NaN(SiMe3)2 followed by treatment with 1 equiv of RECl3 in THF at-78 ? afforded the CNC-pincer rare-earth metal bisamido complexes L2RE[N(SiMe3)2]2(L2 =[4-CH3-2-{CH3-[N(CH)2CN]}C6H3]2N,RE = Y(11),Eu(12),Er(13)).Complexes 11 and 13 can also be obtained by the stepwise reactions of H3L2I2 with 2 equiv n-BuLi in THF for 4 h at-30 ? followed by treatment with[(Me3Si)2N]3RE(?-Cl)Li(THF)3,together with a fused-heterocyclic compound 3,8,9,14-tetramethyl-8a,9-dihydro-8H-benzo[4,5]imidazo[2',1':2,3]imidazo[1,2-a]imid azo[2,1-c]quinoxaline(14)which formed through carbene C-C and C-N coupling.The one-pot reactions of bis[2-(3-isopropylimidazolium)-4-methylphenyl]amine diiodides(H3L3I2)with 5 equiv of NaN(SiMe3)2 followed by treatment with 1 equiv of RECl3 in THF at-78 ? afforded the CNC-pincer rare-earth metal bisamido complexes L3RE[N(SiMe3)2]2(L3 =[4-CH3-2-{(CH3)2CH-[N(CH)2CN]}C6H3]2N,RE=Y(15),Er(16),Yb(17)).Complexes 15-17 can also be prepared by stepwise reactions of H3L3I2 with 2 equiv n-BuLi in THF at-30 ?,followed by reactions with[(Me3Si)2N]3RE(?-Cl)Li(THF)3.The reaction of H3L3I2 with 1 equiv[(Me3Si)2N]3Yb(?-Cl)Li(THF)3,afforded the mixed complexes of L3Yb[N(SiMe3)2]2(17)and an unexpected monoamido ytterbium iodide incorporating the diarylamido bridged bis(isopropyl NHC)based CNC-pincer ligand L3YbI[N(SiMe3)2](18).The catalytic activity of the above rare-earth metal complexes 11-13 and 15-18 towards the addition of the P-H bond of phosphines to heterocumulenes were investigated.The results indicated that all complexes displayed high activity toward the addition of the P-H bond of phosphines to heterocumulenes producing the corresponding phosphaguanidines,phosphaureas and phosphathioureas which represents the first example of the CNC-pincer rare-earth metal amido complexes incorporating the diarylamido bridged bis(methyl or isopryl NHC)ligands as catalysts for the catalytic addition of the P-H bond of phosphines to heterocumulenes with high efficiency in the presence of a low catalyst loading at room temperature,it provides a straightforward,atom-efficient route to preparation of phosphaguanidines,phosphaureas and phosphathioureas.3.Synthesis,structure of rare-earth metal bisamido complexes incorporating a pyridyl ?-ketoiminato schiff base NNO type ligand,and catalytic activity for polymerization of isopreneThe reaction of 4-((2-(pyridin-2-yl)ethyl)imino)pent-2-en-2-ol(21)with 1 equiv of[(Me3Si)2N]3RE(?-Cl)Li(THF)3,gave the rare-earth metal bisamido complexes incorporating a pyridyl ?-ketoiminato shiff base NNO type ligand[LRE{[N(SiMe3)2]2}](L = CH3C(O)=CHC(CH3)=NCH2CH2(2-C5H4N),RE = Y(22),Nd(23),Sm(24),Gd(25),Dy(26)Er(27),Yb(28)).All complexes were fully characterized by elemental and spectroscopic analyses,their structures were determined by single-crystal X-ray diffraction study.Complexes 22-28 as recatalysts for isoprene polymerization were investigated.Results showed that the complexes except for complexes 24 and 28 could initiate the polymerization of isoprene with a high activity to afford polyisoprene with high regio-and stereoselectivity(1,4-cis selectivity up to 96.2%)in the presence of cocatalysts.Results also showed that central metal ion has significant effect on the catalytic activity.