Living polymerization of phenylacetylenes catalyzed by cationic rhodium complexes bearing tetrafluorobenzobarrelene

Binary catalysts composed of cationic rhodium complexes, [(tfb)Rh(L)2]X (tfb: tetrafluorobenzobarrelene, L: phosphine ligand, X: counter anion), and iPrNH2 induced living polymerization of phenylacetylene and its ring-substituted derivatives. For instance, [(tfb)Rh(PPh3)2]BPh4 in conjunction with iPrNH2 polymerized phenylacetylene in a living manner to yield poly(phenylacetylene) with narrow molecular weight distribution (Mw/Mn 1.09) quantitatively. The living nature was confirmed by kinetic plots of the polymerization. Nuclear magnetic resonance studies revealed that iPrNH2 serves to dissociate the coordinating PPh3 ligand of [(tfb)Rh(L)2]X to form an initiating species. Block copolymers were synthesized by the sequential polymerization of different phenylacetylenes using the present catalyst.