Determination of the tacticities of ring-opened metathesis polymers of symmetrical 5,6-disubstituted derivatives of norbornene and norbornadiene from the 13C NMR spectra of their hydrogenated derivatives

Ring-opened metathesis polymers were made from 5,6-di-exo-(carbomethoxy)-norbornene and 5,6-di-(carbomethoxy)-norbornadiene using a variety of catalysts and their C-13 NMR spectra analyzed in detail. These polymers were then fully hydrogenated using diimine and found by C-13 NMR analysis to give with complete selectivity the same saturated derivative. This permitted the tacticities to be assigned in detail and the consistency of the analysis further checked with respect to the m (meso) and r (racemic) line orders identified for all the precursor polymers. While OsCl3/phenylacetylene as catalyst gave high cis syndiotactic polymers OsCl3 by itself formed high trans atactic material; RuCl3 afforded the corresponding trans polymer with a substantial isotactic bias. By way of contrast MoCl5/Me4Sn in dioxan is an excellent catalyst for the synthesis of all cia isotactic poly-5,-di-(carbomethoxy)-norbornadiene. (C) 1998 Elsevier Science B.V. All rights reserved.