Mechanical Activation of Catalysts for C-C Bond Forming and Anionic Polymerization Reactions from a Single Macromolecular Reagent

Abstract

Coupling of pyridine-capped poly(methyl acrylate)s, PyPM (where M corresponds to the number average molecular weight in kDa), to the SCS-cyclometalated dipalladium complex [(1)(CH3CN)2] afforded organometallic polymers [(1)(PyPM)(2)] with a concomitant doubling in molecular weight. Ultrasonication of solutions containing [(1)(PyPM)(2)] effected the mechanical scission of a palladium-pyridine bond, where the liberated PyPM was trapped with excess HBF4 as the corresponding pyridinium salt, harnessed to effect the stoichiometric deprotonation of a colorimetric indicator, or used to catalyze the anionic polymerization of alpha-trifluoromethyl-2,2,2-trifluoroethyl acrylate. The mechanically induced chain scission also unmasked a catalytically active palladium species which was used to facilitate carbon-carbon bond formation between benzyl cyanide and N-tosyl imines. Spectroscopic and macromolecular analyses as well as a series of control experiments demonstrated that the aforementioned structural changes were derived from mechanical forces that originated from ultrasound-induced dissociation of the polymer chains connected to the aforementioned Pd complexes.