The partial hydrolysis of Cp'2ErCl (1) (Cp' = CH3OCH2Ch2C5H4) affords [CP'2Er(mu-OH)]2, the single crystal X-ray structure of which reveals that the complex is dimeric with bridging hydroxide groups. The molecular structure shows the hydroxyl groups bridging with distances Er-O = 2.258(5), 2.216(5) angstrom, and the methoxyethyl group coordinating with distances Er-O(1) = 2.542(3), Er-Cp1 = 2.3981(4) and Er-Cp2 = 2.1680(3) angstrom. The bond angles of O-Er-O* and O-Er-O(1) in 2 are 71.6(2) and 73.2 (2)-degrees, respectively.