The reactivity of [Cp(2)Ln(mu-OH)(THF)](2) (Ln = Y (1), Er (2), Yb (3)) toward PhEtCCO, PhNCO, Cp(3)Ln, [Cp(2)Ln(mu-CH3)](2), and the LiCl adduct of Cp(2)Ln(n)Bu(THF)(x) was examined. In all cases, OH-centered reactivity is observed: complexes 1-3 react with PhEtCCO to form the O-H addition products [Cp(2)Ln(mu-eta(1):eta(2)-O2CCHEtPh)](2) (Ln = Yb (5), Er (6), Y (7), respectively, for 1-3), whereas treatment of 1 with PhNCO affords the addition/CpH-elimination/ rearrangement product [{Cp2Y(THF)}(2)(mu-eta 2:eta(2)-O2CNPh)] (8), which contains an unusual PhNCO2 dianionic ligand. Analogous compound [Cp(2)Ln(THF)](2)(mu-eta(2): eta(2)-O2CNPh) (Ln) Yb (9), Er (10)) and 8 can be obtained in a higher yield by treatment of [Cp(2)Ln(mu-OH)(THF)](2) with PhNCO followed by reaction with the corresponding Cp3Ln. However, attempts to prepare the corresponding heterobimetallic complex by reacting stoichiometric amounts of [Cp2Y(gamma-OH)( THF)](2) with PhNCO followed by treating it with Cp3Yb are unsuccessful. Instead, only rearrangement products 8 and 9 are obtained. Furthermore, the reaction of 3 with [Cp2Yb(mu-CH3)](2) or Cp3Yb forms oxo-bridged compound [Cp2Yb(THF)](2)(mu-O) (11), whereas the reaction of [Cp2ErCl](2) with (LiBu)-Bu-n followed by treatment with 2 affords unexpected mu-oxo lanthanocene cluster (Cp2Er)(3)(mu-OH)(mu(3)-O)(mu-Cl)Li(THF)(4) (12). In contrast to 1 and 2, 3 shows a strong tendency to undergo the intermolecular elimination of CpH at room temperature, giving trinuclear species [Cp-2-Yb( mu-OH)](2)[ CpYb(THF)](mu(3)-O) (4). The single-crystal X-ray diffraction structures of 1, 2, and 4-12 are described. All the results offer an interesting contrast to transition- and main-metal hydroxide complexes.