Acyclic diene metathesis (ADMET) polymerization using a well-defined ruthenium based metathesis catalyst

A series of α,ω-dienes have been exposed to Ru(Cl₂)(CH=Ph)(PCy₃)₂, [Ru] 3, metathesis catalyst under acyclic diene metathesis (ADMET) conditions, and the products were compared with those obtained previously using Schrock's well defined Mo and W alkylidenes. High molecular weight polymers can be synthesized using [Ru] 3 if lower monomer to catalyst ratios (with respect to [Mo] 1 and [W] 2 are used. Monomer structure plays a role since 1,9-decadiene produces molecular weights typical of ADMET chemistry, whereas 1,5-hexadiene produces only oligomers. This decrease in reactivity is attributed to a manifestation of intramolecular π-complexation of the tethered olefin in 1,5-hexadiene polymerizations. Substituents at the 2-position of α,ω-dienes also affects polymerization in that only dimers can be produced from 2-methyl-1,5-hexadiene, a result similar to the same reaction performed with [W] 2. Diallyl ether oligomerizes effectively in the presence of [Ru] 3 with a ratio of cyclics to oligomers comparable to results obtained with [Mo] 1 and [W] 2.