Ru (η6-naphthalene)(η4-1, 5-COD)(1)(10 mol%) catalyzes the tail-to-tail dimerization of methyl methacrylate (MMA) in MeCN in 74% yield at 70° C for 4 h. Without use of solvent complex 1 (1 mol%) rapidly catalyzes the tail-to-tail dimerization and trimerization of MMA in 59% and 23% yields, respectively, at 70° C for 5 min.