Kinetics of initiation and propagation of the metathesis polymerization of the exo diels-alder adduct of cyclopentadiene and maleic anhydride initiated by the tungsten-carbene complex W[ H 2](OCH 2CMe 3) 2Br 2

Abstract

The title reaction was followed by 1H NMR at 277 – 314 K. The initiator (I) adds one molecule of monomer (M) to give a tungsten-carbene species P 1 which then adds further monomer molecules to give P n ( n > 1). P 1 and P n ( n > 1) can be distinguished by their (OCH 2CMe 3) 2 signals at 4.44, 4.39 and 4.46, 4.41 ppm respectively; the two neopentoxy ligands are non-equivalent in each case. [P 1] builds up to a maximum (65% of [I 0]) and then declines. At 294 K the initiator is all consumed after 40 min and [M] then decays according to a first-order law ( t 1 2 = 74 min for [P total] = [I 0] = 5.0 × 10 −2 mol dm −3). The activation energy for the propagation reaction is about 51 kJ mol −1. The initiation rate constant is 3.8 ± 0.2 times as large as the propagation rate constant. The 13C NMR spectrum of the exo, exo-dimethyl ester polymer derived from the polymer of M indicated that the polymer contained 28% cis double bonds. The endo adduct of cyclopentadiene and maleic anhydride was also found capable of adding to the living chain; this is the first report that the endo monomer can undergo metathesis polymerization.