Addition of 1 equiv of ROH to Mo(NAr)(CHCMe2Ph)(Me(2)Pyr)(2) (Ar 2,6-i -Pr2C6H3, Me(2)Pyr = 2,5-dimethylpyrrolyl) in diethyl ether or THF yields Mo(NAr)(CHCMe2Ph)(OR)(Me(2)Pyr) species where R (CH3)(3)C (1, 22% isolated yield), (CH3)(2)CH (2, 83%), Ar (3, 81%), (CF3)(2)CH (4, 45%), or (CF3)(2)(CH3)C (5, 80%). Ring-closing enyne metathesis by various catalysts leads to cyclic products that arise through initial addition of the triple bond to a methylene species (initially neophylidene) to yield an alpha- or a beta-substituted metallacyclobutene intermediate.