INITIATION OF RING-OPENING METATHESIS POLYMERIZATION IN PROTIC MEDIA - EXTENSION OF [RU(H2O)6]2+ CATALYZED POLYMERIZATIONS TO LESS-STRAINED CYCLIC MONOMERS

Ru(II)(H2O)6(tos)2 (tos = p-toluenesulfonate) is an active catalyst for ring-opening metathesis polymerization (ROMP) of norbornene and 7-oxanorbornene derivatives in protic media. The activity of this catalyst can be extended to less reactive monomers, such as cyclooctene and cyclopentene, by the addition of ethyl diazoacetate to serve as an initiator. Due to the polymer/ring equilibrium for this system, the yield of polymer is low. The gel permeation chromatography trace of the product is distinctly bimodal, consisting of a mixture of cyclic oligomers and higher molecular weight polymer. These results show that the difficulty of polymerizing unstrained cyclic olefins in the original ruthenium systems lies in the initiation step and not in the propagation. Although the active catalyst in this system has not been identified, a ruthenium carbene produced from the reaction of ethyl diazoacetate with (PPh3)3RuCl2 has been observed.