| A series of substituted polyacetylenes were synthesized using a set of catalysts based on the cationic complex [L2Pd(CH 3CN)2](BF4)2 (L = CH3CN or PR3). The conjugated polymers derived from the monomers of 1,6-heptadiyne and several mono-substituted alkynes (R = aromatic, alkyl, ester) are desirable for their potential electrical, optical, and gas permeability properties. The employed cationic PdII catalysts are ideal for acetylene polymerization reactions since they are air and water stable, functional group tolerant, and their metal centers are easily accessible by the substrate. The molecular weights of the synthesized polymers were modest (average M n = 3 × 103 g/mol), but their polydispersity indexes were consistently close to monodisperse. Several novel copolymer materials have also been synthesized from combinations of the same monomers. The copolymers were also of modest molecular weight, but their UV-Vis absorptions indicate high degrees of conjugation. Like the homopolymers, the polydispersity indexes of the random copolymers were quite low (<1.5). Mechanistic routes are proposed for this alkyne polymerization system based on a series of coordination and insertion steps. These mechanisms are novel for the [Pd(CH3CN) 4][BF4]2 catalyst and alkyne monomers because they involve a PdIV intermediate. The suggested routes are supported by indirect evidence and by product analysis. The cationic complex [L2Pd(CH3CN)2][BF4]2 (L = [PhP(C6H4SO3Na)2]) was also used in an aqueous catalyst solution in an interfacial polymerization of alkynes. While the yields and molecular weights of the polymers produced on the water surface were low, the concept was successful. The aqueous polymerization occurred using a very dilute concentration of catalyst that was reusable over five cycles. |
