Coordinative Chain Transfer Polymerization of Butadiene with Functionalized Aluminum Reagents

Functionalized aluminum alkyls enable effective coordinative chain transfer polymerization with selective chain initiation by the functionalized alkyl. (omega-Aminoalkyl)diisobutylaluminum reagents (12 examples studied) obtained by hydroalumination of alpha-amino-omega-enes with diisobutylaluminum hydride promote the stereoselective catalytic chain growth of butadiene on aluminum in the presence of Nd(versatate)(3), Cp*Nd-2(allyl), or Cp*Gd-2(allyl) precatalysts and [PhNMe2H+]/[B(C6F5)(4)(-)]. Carbazolyl- and indolylaluminum reagents result in efficient molecular weight control and chain initiation by the aminoalkyl rather than the isobutyl substituent bound to aluminum. As confirmed for (3-(9H-carbazol-9-yl)propyl)-initiated polybutadiene (PBD), for example, by deuterium quenching studies, polymer chain transfer by beta-hydride transfer is negligible in comparison to back-transfer to aluminum.