Fused-ring monomers other than norbornene derivatives

1 Fused ring monomers other than norbornene derivatives 

Compounds in this category are bicyclo[3.3.0]octene (15), tricyclo[5.2.1.0 ]dec-3-ene (16), exo-tricyclo[5.2.1.0 ]dec-8-ene (17), benzvalene (18), and delta-cyclene (19). Of these, 15 and 16 do not undergo ROMP with conventional catalysts (Ofstead 1972), but 17 does so (Oshika 1968). The ROMP of 18 proeeeds smoothly using tungsten carbene initiators, and films of the polymer 18P can be cast directly from the reaction mixture (Swager 1988, 1989). The polymer has a tendency to cross-link and to decompose spontaneously once isolated in dry form, so is best handled in solution, especially as the decomposition can be explosive. The DSC thermogram of the polymer shows an exotherm at 153°C, attributed mainly to isomerization to polyacetylene 20, eqn. (3), and a second exotherm at 

By virtue of its cheapness and ready polymerizability by all metathesis catalysts norbornene (21) has received a great deal of attention. Its ROMP aecording to the first step in sequence (4) was first reported in the open literature by Truett (1960), using TiCl4/LiAl(C7Hi5)4 as catalyst. Evidence for structure 22 came from its ozonolysis to form cis-cyclopentane-l,3-dicarboxylic aeid (23), later borne out by the NMR spectrum (see Table 11.5). 

With TiCl4//-Bu3Al (2/1) as catalyst system the polymer formed shows little unsaturation, but a 1/2 catalyst/cocatalyst ratio gives ring-opened polymer. With Et3Al as cocatalyst the cationic side reactions can be suppressed by the inclusion of a tertiary amine in the reaction mixture (Saegusa 1964 Tsujino 1964, 1965 Winstein 1977). More recently, a number of titanacyclobutane complexes have 

The binuclear complex (RuClCp)2(=CHCH=CPh2) is not very active (Gagne 1992). 

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