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Yang, Ruijie

University of British Columbia

Rubber is a widely used material that plays an essential role in our daily life. However, the challenging reaction conditions make butyl rubber manufacturing very energy-intensive and difficult to control. Brønsted acids are efficient single component initiators for cationic polymerization with a simple functional cation, H⁺. The coordinating force between cations and anions is crucial for developing high-performance initiators. Weakly coordinating anions have moderate interaction force with cations. This thesis will focus on developing functional initiators containing Brønsted acids and weakly coordinating anions. The growth of the field of weakly coordinating anions has mainly relied on p-block elements such as boron, aluminum, phosphorus, and sulfur. Transition metal complexes have rarely been used as weakly coordinating anions. This thesis will show efforts on designing Ta(V)- or Nb(V)-containing steric bulky WCAs for stabilizing functional Brønsted acids. Chapters 2 and chapter 3 have shown eleven cationic initiators. Among all these cationic initiators, two of them contain anions featuring heptacoordinated Ta(V) with pentagonal bipyramid geometry. These are unprecedented Brønsted acids. H(DMF)₂[2.1] contains the [Ta(1,2-O₂C₆Cl₄)₂(1,2–O₂(OH)₂C₆Cl₄)₂(O=CHN(CH₃)₂)]– anion which has two chelated tetrachlorocatechol ligands, two monodentate tetrachlorocatechol ligands and another DMF ligand with an overall charge of was –1. In addition, [H(DMA)]₂[2.2] was isolated and crystallographically characterized. This Brønsted acid features the novel [Ta(1,2-O₂C₆Cl₄)₃(1,2– O₂(OH)₂C₆Cl₄)]²– dianion with three chelated tetrachlorocatechol and only one monodentate tetrachlorocatechol. Although not specifically tested herein, these new Brønsted acids form a foundation for the future design of novel initiators for cationic polymerization

Text

2021-12-02

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/80306

Chemistry

University of British Columbia

UBCV

http://creativecommons.org/licenses/by-nc-nd/4.0/