Nickel(0)-Catalyzed Polycondensation of Silafluorene: Control over Molecular Weight and Polymer Growth Mechanism

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• 作者：Makoto Tanabe ; Shunsuke Iwase ; Kohtaro Osakada
• 刊名：Organometallics
• 出版年：2016
• 出版时间：August 8, 2016
• 年：2016
• 卷：35
• 期：15
• 页码：2557-2562
• 全文大小：460K
• 年卷期：0
• ISSN：1520-6041

文摘

The catalytic polymerization of silafluorenes with [Ni(dmpe)₂] (dmpe = 1,2-bis(dimethylphosphino)ethane) afforded 2,7-dibutoxy-9H-9-silafluorene polymers with a narrow polydispersity (M_w/M_n < 1.1). In an open vessel, the polymerization ceased shortly after complete consumption of the monomer, but transfer of the reaction mixture into a closed system resumed the polymer growth. Polymerization in a closed system with occasional removal of the evolved H₂ furnished soluble polymers with a maximum molecular weight of M_n = 3860. Treatment of a 2,7-dibutoxy-9H-9-silafluorene tetramer with [Ni(dmpe)₂] resulted in the initial formation of a mixture of monomers and trimers, which subsequently transformed into oligomers (Si₁–Si₉). This polymerization involves a preferential dehydrogenative condensation between the monomer and an oligomer relative to that between oligomers, while the presence of H₂ regenerates the monomer after its consumption and thus promotes further polymer growth.