Comparative Study of Polymerization of 2-, 3- and 4-Iodophenylacetylenes with Rh-, Mo- and W-Based Catalysts

Abstract

2-, 3- and 4-Iodophenylacetylenes (IPA) have been polymerized with [Rh(cod)(OCH3)]2 complex in THF (system Rh), MoCl5 in benzene (Mo), WOCl4 in benzene (WB) and WOCl4/Ph4Sn in benzene-dioxane 1 : 1 (WD). All the systems provide poly(iodophenylacetylene)s (PIPA) and diverse amounts of oligomers (mostly cyclic trimers and tetramers) but the system 2-IPA/Rh that provides mostly dimers only. 2-IPA has also been polymerized with MoOCl4/Bu4Sn/EtOH in toluene (Masuda's catalyst system), however, neither living nor pseudo-living polymerization has been observed. The ring-iodine steric effects control the polymerization activity of the Rh and WB systems and the oligomerization activity of the Mo system. The ring-iodine electronic effects are important for the oligomerization activity of the Rh and WB systems and both oligomerization and polymerization activity of the WD system. Both types of the ring-iodine effect are important for polymerization activity of the Mo system. Rh catalyst provides high-cis-transoid, head-to-tail (HT) 3-PIPA that slowly isomerizes in CDCl3 solution to an insoluble trans-polymer. In the case of 4-PIPA, the isomerization is extremely fast upon polymer entering into contact with methanol. On the basis of spectral changes accompanying this isomerization, the Raman band at 1 338 cm-1 is assigned to the presence of HT sequences of both cis-transoid and trans-cisoid type. The other catalysts provide irregular PIPAs with content of both cis units and HT sequences decreasing in order Mo > WD > WB. Solubility of PIPA samples is shown as a result of complex interplay of the ring-iodine position and the polymer microstructure and molecular weight.

New polyacetylenes with aromatic Schiff's base pendant groups by polymerization of benzylidene-ring-substitutedN-benzylidene-4-ethynylanilines with Rh-based catalysts

“…The total solubility (THF, CHCl 3 , C 6 H 6 ) was retained for poly(II) (R = t-Bu), only. The above described decrease in solubility has already been reported for other polyacetylenes prepared with Rh-based catalysts 18,21) , and this phenomenon is most probably connected with a partial polymer isomerization during isolation 18) . In the precipitation polymerizations, polymers always started to precipitate from the reaction mixture since the early stage of polymerization.…”

“…Polymerizations were started by mixing the solution of monomer (490 lmol; i. e., 100 mg in the case of I) in 1.5 mL of THF with solution of catalyst (9.8 lmol, i. e., 4.7 mg in the case of [Rh(cod)OCH 3 ] 2 ) in 1.5 mL of THF. The time course of solution polymerizations (monomers I, II, III) was monitored by SEC 18) . At a given time, a volume of 5 lL was withdrawn from the reaction mixture, diluted with 0.5 mL of THF and the solution injected into SEC columns (injection volume 20 lL).…”

Polymerization of 4-(ferrocenylethynyl)phenylacetylene with transition metal catalysts

“…Higher intensity of this band observed for PFcEPA prepared with W-based catalyst proves the higher extent of p-conjugation in this polymer compared to the PFcEPA prepared with Rh-based catalyst. An analogous dependence of the extent of p-conjugation on the catalyst used in a polymer preparation was observed for poly(iodophenylacetylene)s 33) for which also significant microstructure differences are evident from their Raman and NMR spectra. However, neither Raman nor NMR spectra provide additional evidence on a microstructure diversity of PFcEPA polymers prepared with Rh-and Wbased catalysts.…”

Degradation of Substituted Polyacetylenes and Effect of This Process on SEC Analysis of These Polymers

“…It is notable that also many other poly(phenylacetylene)s with bulky substituents (e.g., -Si(CH) 3 ) in ortho position are quite stable in air (40,43).These polymers stand out by a high extent of π-conjugation, which is ascribed to the increased stiffness of their main chains due to the effect of bulky ortho substituents. They are supposed to render the plane of the phenyl rings perpendicular to the main chain axis making the main chain more planar and better conjugated.…”