Synthesis of electronically modified Ru-based neutral 16 VE allenylidene olefin metathesis precatalysts.

Electronic modifications within Ru-based olefin metathesis precatalysts have provided a number of new complexes with significant differences in reactivity profiles. So far, this aspect has not been studied for neutral 16 VE allenylidenes. The first synthesis of electronically altered complexes of this type is reported.

Alternating ring-opening metathesis copolymerization by Grubbs-type initiators with unsymmetrical N-heterocyclic carbenes.

A series of Ru(IV)-alkylidenes based on unsymmetrical imidazolin-2-ylidenes, that is, [RuCl(2){1-(2,4,6-trimethylphenyl)-3-R-4,5-dihydro-(3H)-imidazol-1-ylidene}(CHPh)(pyridin)] (R = CH(2)Ph (5), Ph (6), ethyl (7), methyl (8)), have been synthesized. These and the parent initiators [RuCl(2)(PCy(3)){1-(2,4,6-trimethylphenyl)-3-R-4,5-dihydro-(3H)-imidazol-1-ylidene}(CHC(6)H(5))] (R = CH(2)C(6)H(5) (1), C(6)H(5) (2), ethyl (3)) were used for the alternating copolymerization of norborn-2-ene (NBE) with cis-cyclooctene (COE) and cyclopentene (CPE), respectively. Alternating copolymers, that is, poly(NBE-alt-COE)(n) and poly(NBE-alt-CPE)(n) containing up to 97 and 91% alternating diads, respectively, were obtained.