Studies On Synthesis And Catalytic Property Of Novel Chromium-Based Catalysts For Ethylene Oligomerization/Polymerization

Chromium-based catalysts are the most important catalysts for ethylene tri-/tetramerization.This dissertation is subject to developing the chromium catalysts bearing the new phosphinoamine ligands.Five charpters are included,which are shown as follows.1.Ethylene tri-/tetramerization catalyzed by the chromium complex bearing N-tetrahydrofurfuryl PNP ligandThe N-tetrahydrofurfuryl diphoshinoamine(PNP)ligand(L1)was synthesized by means of two-step salt elimination reactions in which formation of the two kinds of the aminyl lithium salts was each separatedly conducted for the reaction.The ligand reacted with CrCl3(THF)3 and Cr(CO)6 to give P,P-chelation complexes[{Ph2PN(CH2OC4H7)PPh2}CrCl2(μ-Cl)]2(1)and[Ph2PN(CH2OC4H7)PPh2]Cr(CO)4(2),respectively.Compounds L1,1 and 2 were characterized by NMR spectrum,IR spectra and elemental analysis,of which complex 2 was further confirmed by X-ray crystallography.Upon activation with methylaluminoxane(MAO)or AlEt3,the catalyst systems including 1,2,L1/CrCl3(THF)3,L1/Cr(acac)3 and L1/CrCl2(THF)2 were investigated,which all exhibited good ethylene tri-/tetramerization.The best catalytic activity was achieved by 15.9 kg(product)/g(Cr)h by using 1/MAO,in which selectivity was up to 63.6%for 1-C8 and the total selectivity of 1-Cs and 1-C6 was 74.0%.2.Chromium complexes bearing NNP-framework ligand:synthesis,characterization,and catalytic properties of ethylene tri-/tetramerization and polymerizationThe NNP-framework ligands ArN=C(R)NH(o-Ph2PC6H4)(Ar = 2,4,6-Me3C6H2,R = Ph(L2);Ar = 2,6-iPr2C6H3,R = Ph(L3);Ar = 2,6-iPr2C6H3,R= tBu(L4))were prepared.Ligands L2,L3,and L4 respectively reacted with CrCl3(THF)3,yielding the N,P-chelation complexes[ArNH(R)C=N(o-Ph2PC6H4)]CrCl3(THF)(Ar = 2,4,6-Me3-C6H2,R = Ph(3);Ar = 2,6-iPr2C6H3,R-Ph(4);Ar = 2,6-iPr2C6H3,R = tBu(5)).The ligand lithium salts ArN=C(R)N(o-Ph2PC6H4)Li reacted with CrCl3(THF)3 to produce the N,N,P-chelation complexes[ArN=C(R)N(o-Ph2PC6H4)]CrCl2(THF)(Ar ＝2,4,6-Me3C6H2,R = Ph(6);Ar = 2,6-iPr2C6H3,R = Ph(7)),and with CrCl2(THF)2 to give {[ArN=C(R)N(o-Ph2PC6H4)]Cr(μ-Cl)}2(Ar=2,4,6-Me3C6H2,R = Ph(8);Ar ＝2,6-iPr2C6H3,R = Ph(9);Ar = 2,6-iPr2C6H3,R ＝tBu(10)).Compounds L2-L4 as well as 3-10 were characterized by NMR spectrum,IR spectra and elemental analysis,of which L4,4,7 and 10 were further confirmed by X-ray crystallography.Upon activation with organoaluminum cocatalyst,complexes 3-5 were all catalytically active in ethylene tri-/tetramerization along with polymerization,but complexes 6-10 functioned only in ethylene polymerization.The correlationship between the structure and the catalytic property of the catalyst system is disscussed.3.Chromium catalysts bearing PCnNP-framework ligands:exhibiting the catalytic behaviors varied between polymerization and selective oligomerization of ethyleneA series of chromium complexes[o-Ph2PC6H4(CH2)nN(R)PPh2]CrCl3(THF)(n = 0,R = H(11);n = 0,R = Me(12);n = 1,R = H(13)),[Ph2P(CH2)n-NHPPh2]CrCl3(THF)(n = 2(14);n = 3(15);n = 4(16))and[o-Ph2PC6H4(CH2)nN(R)PPh2]Cr(CO)4(n = 0,R = H(17);n = 0,R = Me(18);n = 1,R = H(19)),[Ph2P(CH2)nNHPPh2]Cr(CO)4(n = 2(20);n = 3(21))bearing asymmetric diphosphine ligands(PCnNP)have been prepared.Complexes 11-21 were characterized by NMR spectrum,IR spectra,magnetic susptibility,EPR spectra and elemental analysis,of which 17,19,20 and 21 were further confirmed by X-ray crystallography.In combination with MAO,the complexes 11,12 and 14 bearing two-carbon spacer ligands promoted the polymerization of ethylene and the best catalytic activity was up to 625 kg(product)/g(Cr)·h,while complexes 13,15 and 16 bearing three-or four-carbon spacer ligands all exhibited selective ethylene tetramerization with a high activity of 110 kg(product)/g(Cr).h and the selectivity of 1-C8 could be improved up to 71.3 wt%.The X-band electron paramagnetic resonance(EPR)spectra and X-ray photoelectron spectroscopy(XPS)were performed to have insight into the active species.4.Chromium catalysts bearing PC3NPN-framework ligands:synthesis,characterization,and catalytic properties of ethylene nonselective oligomerizationA series of chromium complexes[Ph2PCH2CH2CH2NHP(NR1R2)Ph]-CrCl3(THF)(NR1R2 = NC4H4(22);R1 = R2 = Me(23);R1 = R2 = iPr(24);R1 =Me,R2 = Ph(25);R1＝H,R2 = tBu(26))and[Ph2PCH2CH2CH2NHP-(NC4H4)Ph]Cr(CO)4(27)bearing asymmetric diphosphine ligands(PC3NPN)have been prepared.Complexes 22-27 were characterized by NMR spectrum,IR spectra,EPR spectra and elemental analysis,of which complex 27 were further confirmed by X-ray crystallography.In combination with MAO,complexes 22-26 all exhibited nonselective ethylene oligomerization.The best catalytic activity(113 kg(product)/g(Cr)·h)and the least PE(9%)were obtained by complex 26.5.Chromium catalysts bearing PCnNPX-framework ligands:synthesis,characterization,and catalytic properties of ethylene polymerizationA series of chromium complexes[Ph2P(CH2)nNHP(X)Ph]CrCl3(THF)(n = 2,X = pyrrolyl(28);n = 2,X = NMe2(29);n-2,X = NiPr2(30);n = 2,X ＝NMePh(31);n = 2,X = NHtBu(32);n = 2,X = OSiPh3(33);n = 3,X ＝OSiPh3(34))and[Ph2P(CH2)3NHP(OSiPh3)Ph]Cr(CO)4(35)bearing asymmetric diphosphine ligands(PCnNPX)have been prepared.Complexes 28-35 were characterized by NMR spectrum,IR spectra,EPR spectra and elemental analysis,of which 35 was further confirmed by X-ray crystallography.In combination with MAO,complexes 28-34 promoted the polymerization of ethylene.Complex 30 exhibited the best catalytic activity with 369 kg(product)/g(Cr)h.