C-13 NMR-SPECTRA OF TACTIC AND ATACTIC HYDROGENATED RING-OPENED POLYMERS OF ENANTIOMERIC AND RACEMIC ENDO,EXO-5,6-DIMETHYLNORBORNENE

Polymers 1 of the title monomer, prepared using well-defined molybdenu m carbene complexes as catalysts, have been hydrogenated and the struc tures of the resultant polymers 2 examined by C-13 NMR spectroscopy. T he hydrogenated polymer made from the all-cis isotactic polymer of (+) -monomer showed a single set of C-13 NMR lines as expected for an NX s equence of endo (N) and exo (X) substituents. The hydrogenated polymer made from a cis isotactic polymer of (+/-)-monomer showed additional fine structure arising from the random incorporation of both enantiome rs in the isotactic polymer chain: four equal lines for C-9 (orientati onal triad sensitivity), two equal lines for C-3, C-4, C-5, and C-1 (d yad sensitivity), but single lines for C-8, C-2, C-7 and C-6 (insensit ive to the relative orientation of adjacent repeating units). The hydr ogenated polymer made from a trans atactic polymer of (+)-monomer show ed fine structure due to the presence of both In and r dyads. That mad e from a trans atactic polymer of (+/-)-monomer contains 16 possible t riad sequences and gave a mon complicated spectrum. A complete assignm ent was made for the first three poly mers and a partial assignment fo r the fourth. Polymers made using non-carbene catalysts were also exam ined. Hydrogenation of an all-trans precursor made from (+/-)-monomer using RuCl3 as catalyst gave an atactic polymer, confirming previous o bservations. Hydrogenation of a 61% cis, cis/trans blocky precursor, m ade from (+)-monomer using OsCl3/PhC drop CH as catalyst, gave a syndi otactic-biased stereoblocky polymer, indicating a c/r, t/m correlation in the precursor polymer.