Reactivity Of Rare-Earth Metal Alkyl Compounds With 2- Or 3-Functionalized Indoles.Synthesis,Reactivity And Catalytic Performances Toward Isoprene Polymerization Of Novel Rare-Earth Alkyl Complexes Having Indolyl Ligands

The dissertation focused on the reactivity and coordination chemistry of the rare-earth metal alkyl compounds RE(CH2Si Me3)3(THF)2 with 2-(aromatic)imino or amino-functionalized indoles and 3-(aliphatic)imino or amino-functionalized indoles.The reactivity and catalytic activity toward isoprene polymerization of the resulting new rare-earth metal alkyl complexes with indolyl ligands were also studied.The dissertation is made up of the following four parts: 1)the reactivities of the rare-earth metal alkyl complexes with 2-[(N-2,6-diisopropylphenyl)iminomethylene)]indole and the catalytic activities of resulting complexes toward isoprene polymerization;2)the reactivities of the rare-earth metal alkyl compounds RE(CH2Si Me3)3(THF)2 with 2-[(N-2,6-diisopropylphenyl)aminomethyl]indole and the catalytic activities of the corresponding complexes toward isoprene polymerization;3)the reactivities of the rare-earth metal alkyl compounds RE(CH2Si Me3)3(THF)2 with 2-[(N-tert-butyl)iminomethylene)]indole and the catalytic activities of the new complexes toward isoprene polymerization;4)the reactivities of the rare-earth metal alkyl complexes with 3-[(N-tert-butyl)aminomethyl]indole and the catalytic activities of the new complexes toward isoprene polymerization;The details are described as follows.(1)The reactivities of rare-earth metal alkyl compounds RE(CH2Si Me3)3(THF)2with 2-[(N-2,6-diisopropylphenyl)iminomethylene)]indole and the catalytic activities of resulting complexes toward isoprene polymerizationReactions of 2-[(N-2,6-diisopropylphenyl)iminomethylene)]indole 2-(2,6-i Pr2-C6H3N=CH)C8H5NH(1)with [RE(CH2Si Me3)3(thf)2] afforded the rare-earth metal alkyl complexes [?1:?1-2-(2,6-i Pr2C6H3N=CH)Ind]2RE(CH2Si Me3)(thf)(Ind = indolyl,RE = Yb(2),Er(3.),Y(4),Dy(5),Gd(6)).The samarium complex [?1:?1-2-(2,6-i Pr2-C6H3N=CH)Ind]3Sm(7)without alkyls was produced when the rare-earth metal ion is larger ionic radii Sm.Reaction of complex 3 or 4 with Ph Si H3 not afforded the corresponding hydride complexes,instead novel dinuclear complexes {[?-?6:?1:?1-2-(2,6-i Pr2C6H3NCH2)Ind]RE[2-(2,6-i Pr2C6H3N=CH)Ind]}2(Ind = indolyl,RE = Er(8),Y(9))with one of the CH=N double bonds were reduced to the C-N single bond,meanwhile,the coordination modes of the indoly ligands with rare-earth metal have been changed refer to those in complexes 3 and 4.The reactivities of complex 3 or 4 with aromatic amidine(2,6-i Pr2C6H3)N=CHNH(2,6-i Pr2C6H3)were also studied with isolation of corresponding complexes [?1:?1-2-(2,6-i Pr2C6H3N=CH)C8H5N]2RE[(2,6-i Pr2C6H3)-N=CHN(2,6-i Pr2C6H3)](RE = Er(10),Y(11))with amidinate ligand [(2,6-i Pr2C6H3N)2CH]-.The molecular structures of all complexes have been determined by X-ray crystallographic analyses.The rare-earth metal monoalkyl complexes 2-6 have been tested as isoprene polymerization initiators.It is found that the catalytic system composed of the monoalkyl complexes,Al i Bu3 and [Ph3C][B(C6F5)4] can polymerize isoprene with a high catalytic activity and high 1,4-cis-selectivity.The ionic radii of the complexes have a great influence on the catalytic activity of the polymerization.The catalytic activity will increase with the increase of the ionic radii of the complexes.The highest one is the gadolinium complex among the monoalkyl complexes investigated.The optimum combination 5/Al i Bu3/[Ph3C][B(C6F5)4] displayed a high catalytic activity for isoprene polymerization producing polymers with an extremely high 1,4-cis-selectivity(up to 99%),a high number-average molecular weight(M n = 7.2 × 105),and a narrow molecular weight distribution(PDI = 1.34)at the isoprene-to-initiator molar ratio of 6000:1.To the best of our knowledge,it represents the first example of mononuclear rare-earth monoalkyl catalytic systems to display catalytic activity at such a low catalyst loading.The result should be attributed to the perfect unity of the steric and electronic effects of the electron-rich indolyl ligand and gadolinium effect.A possible polymerization mechnism was proposed on the basis of the experiment and documented results.(2)The reactivities of rare-earth metal alkyl compounds RE(CH2Si Me3)3(THF)2with 2-[(N-2,6-diisopropylphenyl)aminomethyl]indole and the catalytic activities of resulting complexes toward isoprene polymerizationReactions of 2-(2,6-i Pr2C6H3NHCH2)C8H5NH with RE(CH2Si Me3)3(THF)2produced a series of rare-earth metal complexes with indolyl ligand having diversified structures depending on the ionic radii of rare-earth metals.When the central ion is smaller Yb,reaction of 2-(2,6-i Pr2C6H3NHCH2)C8H5NH with RE(CH2Si Me3)3(THF)2at room temperature generated mononuclear ytterbium complex [?1:?1-2-(2,6-i Pr2C6 H3N=CH)Ind]2RE(II)(thf)2(RE = Yb(13))having imino-functionalized indolyl ligands in ?1:?1 mode with the reduction of ytterbium(III)to ytterbium(II)and the oxidation of amino to imino group.When the rare-earth metal ions are Er and Y with a larger ionic radius than Yb,reactions of 2-(2,6-i Pr2C6H3NHCH2)C8H5NH with RE(CH2Si Me3)3(THF)2 produced dinuclear erbium and yttrium complexes {[m-?2:?2:?1-2-(2,6-i Pr2C6H3NCH2)Ind]RE-(CH2Si Me3)(thf)}2(RE = Er(14a),Y(14b))having indolyl ligands in m-?2:?2:?1modes with central metals.While the same reactions afforded the novel mixed ligated dinuclear dyprosium complex [(m-?5:?1:?1)-2-(2,6-i Pr2C6H3NCH2)Ind-(m-?6:?1:?1)-2-(2,6-i Pr2C6H3NCH2)Ind][Dy(CH2Si Me3)(thf)]2(15a)having indolyl ligands in m-?5:?1:?1 and m-?6:?1:?1 modes with central metals,and its isomer {[m-?5:?1:?1-2-(2,6-i Pr2C6H3NCH2)Ind]Dy(CH2Si Me3)(thf)}2(15b)having indolyl ligands in m-?5:?1:?1 modes with central metals,when the rare-earth metal is Dy with larger ionic radii than Er and Y.When rare-earth metal is Gd,which has larger ionic radii than Dy,the reaction only produced the mixed ligated dinuclear gadolinium complex [(m-?5:?1:?1)-2-(2,6-i Pr2C6H3NCH2)Ind-(m-?6:?1:?1)-2-(2,6-i Pr2C6H3NCH2)Ind][Gd(CH2Si Me3)(thf)]2(16a),which has the same structure to complex 15 a.Treatment of 5 equiv.of [Gd(CH2Si Me3)3(thf)2] with 4 equiv.of 2-(2,6-i Pr2C6H3NHCH2)C8H5NH,the oxo-bridged trinuclear rare-earth metal complex [(m-?3:?2:?1:?1)-2-(2,6-i Pr2C6H3NCH2)Ind-(m-?2:?1:?1)-2-(2,6-i Pr2C6H3NCH2)Ind-(?1:?1)-2-(2,6-i Pr2C6H3NCH2)Ind]Gd3[(m3-O(CH2)5Si Me3)(m2-O(CH2)5Si Me3)(thf)3](16b)having indolyl ligands in different hapticities with central metals was isolated.The most obvious is that complex 16 b has a unique indolyl ligand bonding with metal in m-?3:?2:?1 modes with the sp2 C–H activated at the 7-indolyl position.When the central ion is Sm with much larger ionic radii than Gd,the reaction of 2-(2,6-i Pr2C6H3NHCH2)C8H5NH with RE(CH2Si Me3)3(THF)2 at room temperature afforded a novel dinuclear samarium complex formulated as [m-?3:?1:?1-2-(2,6-i Pr2C6 H3NCH2)Ind]3Sm2(thf)3(17)having a bridged indolyl ligand in the novel m-?3:?1:?1hapticities.The dinuclear rare-earth metal alkyl complexes can polymerize isoprene upon activation with Al i Bu3 and [Ph3C][B(C6F5)4].The regioselectivity for isoprene polymerization is tunable from 1,4-cis(up to 93.5%)to 3,4-(up to 86.2%)by these catalysts simply by adjusting the addition order of Al i Bu3 and [Ph3C][B(C6F5)4] in the different solvents.(3)The reactivities of rare-earth metal alkyl compounds RE(CH2Si Me3)3(THF)2with 2-[(N-tert-butyl)iminomethylene)]indole and the catalytic activities of resulting complexes toward isoprene polymerizationReactions of RE(CH2Si Me3)3(THF)2 with 3-(t-Bu N=CH)C8H5NH(18)in THF gave a series of novel centrosymmetric dinuclear rare-earth metal alkyl complexes trans-{[m-?2:?1-?1-3-(t-Bu N-CH(CH2Si Me3))Ind]RE(THF)(CH2Si Me3)}2(Ind = Indolyl,RE = Y(19),Dy(20),Yb(21))having indolyl ligands in m-?2:?1-?1 modes with central metals.In the process,the deprotonation of indole and the imino C=N insertion into a rare-earth metal alkyl bond happened producing a new tert-butylamido appended indolyl ligation system.The reactivities of complex 19 with N,N'-dicyclohexylcarbodiimide afforded a centrosymmetric dinuclear yttrium complex trans-{[m-?3:?1-3-(t Bu N(C(NCy)2)-CH(CH2Si Me3))Ind]Y-?3-((NCy)2CCH2 Si Me3)}2(22)with two planes of indolyl motif still parallel.In the process,the imino C=N not only inserted into the yttrium-alkyl bond(Y-C bond),but also the yttrium-amido bond(Y-N bond),affording the amidinated yttrium complex.The dinuclear monoalkyl complexes 19-21 have been tested as isoprene polymerization initiators.It is found that the catalytic system composed of rare-earth metal alkyl complexes,Al i Bu3 and [Ph3C][B(C6F5)4] can polymerize isoprene with a high catalytic activity and high 1,4-cis-selectivity(up to 99.1%).The ionic radii of central metal of the complexes have a great influence on the catalytic activity of the polymerization.The ytterbium complex showed no activity for the isoprene polymerization,owing to its reducible nature.The dyprosium and yttrium complexes having central metal ions with relative larger ionic radii displayed a high catalytic activity and an extremely high 1,4-cis-selectivity(up to 99%)for isoprene polymerization,meanwhile somewhat living properties of the catalytic system were found.(4)The reactivities of rare-earth metal alkyl compounds RE(CH2Si Me3)3(THF)2with 3-[(N-tert-butyl)aminomethyl]indole,and the catalytic activities of corresponding complexes toward isoprene polymerizationReactions of RE(CH2Si Me3)3(THF)2 with 3-(t Bu NHCH2)C8H5NH(23)afforded a series of unexpected trinuclear rare-earth metal monoalkyl complexes [?2:?1-m-?1-3-(t Bu NCH2)Ind]4RE3(thf)5(CH2Si Me3)(RE =Er(24),Y(25),Dy(26))having indolyl ligands in ?2:?1-m-?1 modes.When rare-earth metal is Yb with smaller ionic radii,the same reaction afforded the novel dinuclear ytterbium alkyl complexes having different orientation of six-membered ring of indolyl motifs trans-{[m-?2:?1-?1-3-(t-Bu NCH2)Ind]Yb(THF)(CH2Si Me3)}2(27a,major)and its isomer cis-{[m-?2:?1-?1-3-(t-Bu NCH2)Ind]Yb(THF)(CH2Si Me3)}2(27b,minor),which have indolyl ligands in m-?2-?1:?1 modes.The one-pot reactions of [RE(CH2Si Me3)3(thf)2] with 1 equiv.of 3-(t Bu NHCH2)C8H5NH in THF,followed by treatment with 1 equiv.of amidine [(2,6-i Pr2C6H3)N=CHNH(C6H3i Pr2-2,6)] produced the dinuclear rare-earth metal complexes [?1-?-?1:?1-3-(t Bu NCH2)Ind][?1-?-?1:?3-3-(t Bu NCH2)Ind]RE2(thf)[(?3-2,6-i Pr2C6H3)NCHN(C6H3i Pr2-2,6)]2(RE = Er(28),Y(29)having the indolyl ligands bonding with rare-earth metal in(?1-?-?3:?1 and ?1-?-?1:?1)fashions for the different coordination environment around the central metals.The catalytic performance of the trinuclear and dinuclear rare-earth metal alkyl complexes 24-27 have been tested as isoprene polymerization initiators.It is found that the catalytic system composed of the trinuclear monoalkyl complexes,Al i Bu3 and [Ph3C][B(C6F5)4] can polymerize isoprene with a high catalytic activity and high 1,4-cis-selectivity(up to 98.0%).