Univalent Gallium Salts of Weakly Coordinating Anions: Effective Initiators/Catalysts for the Synthesis of Highly Reactive Polyisobutylene

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• 作者：Martin R. Lichtenthaler ; Alexander Higelin ; Anne Kraft ; Sarah Hughes ; Alberto Steffani ; Dietmar A. Plattner ; John M. Slattery ; Ingo Krossing
• 刊名：Organometallics
• 出版年：2013
• 出版时间：November 25, 2013
• 年：2013
• 卷：32
• 期：22
• 页码：6725-6735
• 全文大小：431K
• 年卷期：v.32,no.22(November 25, 2013)
• ISSN：1520-6041

文摘

The scope of the univalent gallium salts [Ga(C₆H₅F)₂]⁺[Al(OR^F)₄]^{鈭?/sup> and the new completely characterized [Ga(1,3,5-Me₃C₆H₃)₂]+[Al(ORF)₄]鈭?/sup> (RF = C(CF₃)₃) was investigated in terms of initiating or catalyzing the synthesis of highly reactive poly(2-methylpropylene)鈥攈ighly reactive polyisobutylene (HR-PIB)鈥攊n several solvents. A series of polymerization reactions proved the high efficiency and quality of the univalent gallium salts for the polymerization of isobutylene. The best results were obtained using very low concentrations of [Ga(C₆H₅F)₂]+[Al(ORF)₄]鈭?/sup> (down to 0.007 mol%) while working at reaction temperatures of up to 卤0 掳C and in the noncarcinogenic and non-water hazardous solvent toluene. Under these conditions, HR-PIB with an 伪-content of terminal olefinic double bonds up to 91 mol% and a molecular weight of 1000鈥?000 was obtained in good yields. Upon changing [Ga(C₆H₅F)₂]+[Al(ORF)₄]鈭?/sup> for the electron richer [Ga(1,3,5-Me₃C₆H₃)₂]+[Al(ORF)₄]鈭?/sup>, polymerization temperatures could be increased to +10 掳C. The reactivity of the gallium(I) cations therefore seems to be tunable through ligand exchange reactions. Experimental results, density functional theory calculations, and mass spectrometric investigations point toward a coordinative polymerization mechanism.}