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 studied in metathesis of unsaturated esters. WCl6 and WCl5(OAr), where Ar-p-chlorophenyl and p-t-butylphenyl were found to be active in ring opening metathesis of 5-norbornene-2-yl acetate (NBEAc) and in copolymerization of NBEAc with dicyclopentadiene (DCPD). Completely soluble copolymers were prepared in the latter case and copolymerization parameters r1 = r2 = 1 were found. Cometathesis of DCPD with methyl undecenoate 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 DCPD polymerization was studied using definite additions of methyl palmitate (MP). With increasing amounts of MP, reduction of polymerization rate and, significantly, growth of the non-crosslinked polymer fraction occur. Although hydrocarbons with highly strained norbornene ring are necessary for the formation of catalytic active centres, catalytic activity 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 presence of esters.