Synthesis of End‐Functionalized Polyacetylenes that Contain Polar Groups by Employing Well‐Defined Palladium Catalysts

Abstract

A series of [(dppf)PdBr(R)]-type complexes (dppf=1,1'-bis(diphenylphosphino)ferrocene; R=p-cyanophenyl (1 a), o-hydroxymethylphenyl (1 b), and triphenylvinyl (1 c)), in combination with silver trifluoromethanesulfonate (AgOTf), were demonstrated to be active for the polymerization of monosubstituted polar acetylene monomers HC≡CCONHC(4)H(9) (2), HC≡CCO(2)C(8)H(17) (3), HC≡CCH(2)OCONHC(6)H(13) (4), HC≡CCH(2)OCO(2)C(6)H(13) (5), and HC≡CCH(CH(3))OH (6). The yields and molecular weights of the polymers depended on the combination of the Pd catalyst and monomer that was employed. Matrix-assisted laser-desorption/ionization-time of flight (MALDI-TOF) mass spectrometric analysis indicated the formation of polymers that contained the "R" and "H" groups at the chain ends. IR spectroscopic analysis supported the R-end-functionalization of the polymers. NMR spectroscopy and MS identified the presence of species that were formed by single, double, and triple insertion of the monomers into the Pd-C(6)H(4)-p-CN bond, thereby giving solid evidence for an insertion mechanism for the present system. Density functional theory (DFT) calculations suggested the preference for 1,2-insertion of the monomer compared to 2,1-insertion.

New Approach to the Polymerization of Disubstituted Acetylenes by Bulky Monophosphine-Ligated Palladium Catalysts

“…Rh catalysts efficiently polymerize monosubstituted acetylenes to give the corresponding polymers featuring a high cis double bond content, which is associated with the coordination–insertion mechanism. ,,,, A large body of evidence demonstrates that Pd catalysts also yield cis-stereoregulated monosubstituted acetylene polymers through the coordination–insertion mechanism. − Together with the background for the polymerization of monosubstituted acetylenes by Pd and Rh catalysts, the high cis content of poly( 4 )- 1 suggests that the Pd catalysts in the present work follow the coordination–insertion mechanism, in contrast to the metathesis mechanism featured representatively by Mo catalysts. , We attempted to give further support to this proposal by analyzing a mixture of a stoichiometric reaction between 4 and 1 /AgOTf using mass spectrometry, as well as 31 P and 1 H NMR spectroscopies (Scheme ).…”

Novel Route to Cationic Palladium(II)–Cyclopentadienyl Complexes Containing Phosphine Ligands and Their Catalytic Activities

“…The thermal stability of compound 3 in the polymerization of phenylacetylene, therefore, was modest. Gel permeation chromatography curves ( Figures S95–S100, SI ) of the obtained PPAs at 25–50 °C displayed bimodal distribution, which is characteristic of Pd initiators [ 93 , 99 , 101 , 107 , 108 ]. The effect of reaction time on conversion, activity, and molecular weight is summarized in the entries in Table 5 .…”

Synthesis of Arylpalladium(II) Complexes Derived from Benzyl Alcohol, Reactivity toward Alkyl Halides, and Synthesis of Dinuclear Arylpalladium(II) Complexes

“…In view of these results, we decided to extend our research to ortho -palladated hydroxy­methylphenyl complexes, to investigate how the methylene link in the alcoholic substituent would affect the reactivity of the complexes. 2-Hydroxymethylphenyl palladium complexes with a dppf ligand (dppf = 1,1′-bis­(diphenylphosphino)­ferrocene) have been used as catalysts to build end-functionalized polyacetylenes . There has also been a report on oxapalladacycles derived from 2-hydroxymethylbenzene and their use as precatalysts in Heck and cross-coupling reactions .…”