New reactions and new cocatalysts in homogeneous Ziegler-Natta catalysis.

摘要

A series of zirconium and lanthanide metallocene catalysts effect regioselective {dollar}beta{dollar}-alkyl shift-based ring-opening polymerizations of strained exo-methylenecycloalkanes. Methylenecyclobutane (MCB) affords the polymer ({dollar}rm CHsb2CHsb2CHsb2C(CHsb2){dollar}) {dollar}sb{lcub}rm n{rcub}{dollar} under catalysis by (1,2-Me{dollar}sb2{dollar}Cp){dollar}sb2{dollar}ZrMe{dollar}sp+{dollar}MeB(C{dollar}sb6{dollar}F{dollar}sb5)sb3sp-{dollar}, and methylenecyclopropane (MCP) affords the polymer {dollar}lbrackrm CHsb2CHsb2C(CHsb2)rbracksb{lcub}n{rcub}{dollar} under catalysis by {dollar}lbrackrm(Mesb5Cp)sb2LuHrbracksb2{dollar}. Catalysts {dollar}lbrackrm (Mesb5Cp)sb2SmHrbrack sb2{dollar} and {dollar}lbrackrm(Mesb5CP)sb2LaHrbracksb2{dollar} yield 1,2-dimethylene-3-methylcyclopentane (DMP), a dimer of MCP. The mechanism of dimerization is proposed to involve the intermediate 3-methylene-1,6-heptadiene (MHD), which then cyclizes. Catalyst {dollar}rm(Mesb5Cp)sb2ZrMesp+MeB(Csb6Fsb5)sb3sp-{dollar} catalyzes the polymerization of MCP to a polyspirane consisting of 1,3-interlocked five-membered rings (poly(1,4:2,2-butanetetrayl), {dollar}rm(Csb4Hsb6)sb{lcub}n{rcub}).{dollar} The reaction pathway is proposed to consist of {dollar}beta{dollar}-alkyl shift-based ring-opening followed by an intramolecular insertive, ring-closing "zipping-up" process. All of the zirconocene catalysts catalyze selective ring-opening MCB coplymerization with ethylene, to afford polymers {dollar}{lcub}lbrack rm CHsb2CHsb2rbracksb{lcub}x{rcub}lbrack CHsb2CHsb2CHsb2C(CHsb2)rbrack y{rcub}sb{lcub}n{rcub}{dollar}-Lanthanide complexes catalyze selective ring-opening MCP coplymerization with ethylene, to afford polymers {dollar}rm{lcub}lbrack CHsb2CHsb2rbrack sb{lcub}x{rcub}lbrack CHsb2CHsb2C(CHsb2)rbracksb{lcub}y{rcub}{rcub}sb{lcub}n{rcub}.{dollar}; Two soluble weakly coordinating derivatives of the tetrakis(perfluoroaryl)borate anion, B(4-C{dollar}sb6{dollar}F{dollar}sb4{dollar}TBS){dollar}sb4sp-{dollar} and B(4-C{dollar}sb6{dollar}F{dollar}sb4{dollar}TIPS){dollar}sb4sp-{dollar} (TBS = t-butyldimethylsilyl and TIPS = triisopropylsilyl), are synthesized. Reaction of the trityl salts of these anions with dimethyl zirconocenes and thorocenes affords the ion-paired cationic methyl complexes L{dollar}sb2{dollar}MMe{dollar}sp+{dollar}X{dollar}sp-{dollar} (L2 = biscyclopentadienyl type ligand), or in some cases, the hydrido complexes {dollar}rm Lsb2MHsp+Xsp-{dollar} when the reaction is carried out under dihydrogen. The {dollar}rm B(Csb6Fsb5)sb4sp-{dollar}-based zirconocenium methyl complexes {dollar}rm Lsb2ZrMesp+{dollar} are not stable at room temperature with respect to intramolecular C-H activation of the ligand framework. The coordinative tendencies of {dollar}rm MeB(Csb6Fsb5)sb3sp-{dollar}, {dollar}rm B(Csb6Fsb5)sb4sp-, B(Csb6Fsb4TBS)sb4sp-{dollar} and {dollar}rm B(Csb6Fsb4TIPS)sb4sp-{dollar} with respect to the cation are estimated from solution spectroscopic information and the structural dynamics of the ion pairs, and follow the order: {dollar}rm MeB(Csb6Fsb5)sb3sp-, > B(Csb6Fsb4TBS)sb4sp-, approx B(Csb6Fsb4TIPS)sb4sp- > B(Csb6Fsb5)sb4sp-{dollar}. Coordination of the solvent molecules and the neutral metallocenes is found to compete with anion coordination. The thermal stabilities and olefin polymerization activities of the {dollar}rm B(Csb6Fsb5)sb4sp-{dollar}-, {dollar}rm B(Csb6Fsb4TBS)sb4sp-{dollar}-, and {dollar}rm B(Csb6Fsb4TIPS)sb4sp-{dollar}-derived catalysts are greater than those of the corresponding MeB(C{dollar}sb6{dollar}F{dollar}sb5)sb3sp-{dollar}-derived analogues.