First Controlled Cyclopolymerization of Diethyl Dipropargylmalonate by MoCl5−n-Bu4Sn−EtOH−Quinuclidine and MoOCl4−n-Bu4Sn−EtOH−Quinuclidine To Give Highly Regular Polyenes Consisting Exclusively of 1,2-(Cyclopent-1-enylene)−Vinylene Units

Abstract

Diethyl dipropargylmalonate (DEDPM) was cyclopolymerized by MoCl5−n-Bu4Sn−EtOH−quinuclidine (1:1:5:1) and MoOCl4−n-Bu4Sn−EtOH−quinuclidine (1:1:2:1), respectively, to produce poly(DEDPM) exclusively based on 1,2-(cyclopent-1-enylene)vinylene units (EtOH = ethanol). The exact ratio of five- to six-membered rings was determined by quantitative 13C NMR measurements. The initiator efficiency of MoOCl4−n-Bu4Sn−EtOH−quinuclidine (1:1:2:1) was as high as 91%, the highest value ever reported for such systems, whereas the efficiency for the corresponding MoCl5-based initiator was ≤67%. The absorption maximum λmax for poly(DEDPM) was 587 nm. A maximum effective conjugation length (Neff) of 49 was estimated therefrom. Molecular weights and polydispersity indices (PDIs) of the polymers were determined in CHCl3 by size exclusion chromatography (SEC) vs polystyrene (PS). Additionally, light-scattering (LS) data were collected at λ = 690 nm in order to calculate absolute molecular weights. Polydispersities ≤1.9 were obt...