A family of titanium amino-phenolate complexes have been used as mediators in the polymerization of methyl methacrylate, achieving exceptional control without the need for any co-catalyst or activator. Titanium is an attractive metal for applications in organic synthesis and catalysis due to its natural abundance and biocompatibility. To date, the use of titanium complexes in controlled radical polymerization has received relatively little attention, especially in comparison with other first-row transition metals. Here, we report on the synthesis of a variety of substituted titanium(III) amino-phenolate complexes, and the use of these complexes as mediators in the polymerization of methacrylates. Well-controlled polymerizations were achieved, with linear first-order kinetics and dispersities as low as 1.09. The nature of the substituents on the ligand greatly affects the tacticity of the resultant polymer. Detailed experimental and computational studies suggest that the polymerization mechanism is not radical or ionic, but instead proceeds through a coordinating-type mechanism. This likely represents the first example of the initiation of a coordination polymerization with a conventional azo initiator, without the need for pyrophoric (e.g. MAO) or expensive arylboron activators.

Titanium amino-phenolate complexes in controlled methacrylate polymerization

256th National Meeting (2018)

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