Copper-based ATRP catalysts of very high activity derived from dimethyl cross-bridged cyclam

Dimethyl cross-bridged cyclam (DMCBCy) forms a very reducing CuI complex that possesses the highest known catalytic activity to date in atom transfer radical polymerization (ATRP) reactions. The value of the ATRP equilibrium constant in a reaction with methyl chloroacetate for CuICl/DMCBCy is 30-fold larger than for the very active catalyst CuICl/Me6TREN. The activation rate constant for the DMCBCy-based complex was also determined and is about 1.5 times larger than for CuICl/Me6TREN. The ATRP of n-butyl acrylate mediated by CuIBr/DMCBCy was fast even at 30 °C and yielded well-defined polymers when a sufficient amount (about 10 mol% of the total catalyst) of deactivator (CuIIBr2/DMCBCy) was added to the reaction mixture. Side reactions such as electron transfer from the very reducing CuIBr/DMCBCy to the electrophilic acrylate radicals most likely account for the observed limited conversions.

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