COMETATHESIS OF DICYCLOPENTADIENE WITH ESTERS OF UNSATURATED CARBOXYLIC-ACIDS BY HIGH-VALENT TUNGSTEN CHLORIDES AS UNICOMPONENT CATALYSTS

Activity of WCl6, WCl5(OAr) and WOCl4 as unicomponent catalysts was st udied in metathesis of unsaturated esters. WCl6 and WCl5(OAr), where A r-p-chlorophenyl and p-t-butylphenyl were found to be active in ring o pening metathesis of 5-norbornene-2-yl acetate (NBEAc) and in copolyme rization of NBEAc with dicyclopentadiene (DCPD). Completely soluble co polymers were prepared in the latter case and copolymerization paramet ers r1 = r2 = 1 were found. Cometathesis of DCPD with methyl undecenoa te and dimethyl 3-hexenedioate leads to the formation of low molecular weight polymer and/or oligomers containing 1 or 2 ester groups in the molecule. Effects of ester groups on catalytic activity of WC16 in DC PD polymerization was studied using definite additions of methyl palmi tate (MP). With increasing amounts of MP, reduction of polymerization rate and, significantly, growth of the non-crosslinked polymer fractio n occur. Although hydrocarbons with highly strained norbornene ring ar e necessary for the formation of catalytic active centres, catalytic a ctivity of centres already formed is not restricted on the substrates with such a ring. However, their reactivity depends on the ring strain considerably and this substrate selectivity still increases in the pr esence of esters.