Polymerization of o-trifluoromethyl(phenylacetylene) initiated by [Rh(norbornadiene)Cl]2 and MoOCl4-n-Bu4Sn-EtOH catalysts.: Formation of order and disorder trans sequences

o-Trifluoromethyl(phenylacetylene) (oTFMPB) was successfully polymerized by a Rh complex, [Rh(norbornadiene)Cl](2) catalyst, in the presence of triethylamine as the polymerization solvent under mild conditions. Structural differences between the Rh polymer and the Mo polymer prepared with a metathesis initiator, MoOCl4-n-Bu4Sn-EtOH, using the same monomer were compared using laser Raman, H-1 and F-19 NMR, solution and diffuse reflective UV, and electron spin resonance (ESR) methods. The Rh complex produces the aromatic polyacetylene bearing regular head-to-tail, ordered trans sequences where more mobile unpaired electrons generated through the rotational scission of the cis C=C bonds are stabilized, although the Rh catalyst is known to selectively generate the cis-transoid isomer. The Mo-based initiators produce also complete trans-transoid polyacetylene involving irregular head-to-head and/or tail-to-tail units of ca. 32% disordered trans sequences, where less mobile unpaired electrons are stabilized in the irregular trans sequences, although the Mo initiators are known to produce cis-rich polyacetylenes.