Ruthenium metathesis catalysts containing chelating aryloxide ligands

Olefin metathesis catalysts containing chelating aryloxide donors, RuXX'(IMes)(py)(=CHPh) (5, XX' 3,5-dichloro-2-oxidobenzenesulfonate; 6, XX' = catecholate), are accessible in high yield by reaction of o-sulfonato aryloxide or catecholate salts, respectively, with RuCl2(IMes)(py)(2)(=CHPh). Isomerization to pi-bound aryloxides, as found with phenoxide ion or 2'-(diphenylphosphino)-1,1'-binaphthyl-2-olate, is suppressed by use of these smaller, more rigid, chelate rings. Preliminary investigations indicate that the catecholato derivative exhibits metathesis activity approaching that of the recently reported, highly active catalyst RUCl(OC6Br5)(IMes)(py)(=CHPh).