Functionally substituted cyclopentadienyltricarbonylmethyl derivatives of chromium, molybdenum, and tungsten have been prepared and their chemistry studied. The functional groups include carbomethoxy, acetyl, and formyl. The acetyl and formyl derivatives for molybdenum and tungsten were converted into their respective vinyl analogs with methylenetriphenylphosphorane. (η5-Carboxycyclopentadienyl)tricarbonylmethyltungsten was prepared from (η5-carbomethoxycyclopentadienyl)tricarbonylmethyltungsten using potassium hydroxide in methanol. The pKa of this carboxylic acid was determined to be 4.5.