The synthesis of lanthanide hydroxo complexes stabilized by a carbon-bridged bis(phenolate) ligand 2,2'-methylene-bis(6-tert-butyl-4-methylphenoxo) (MBMP2-) was described, and their reactivity toward phenyl isocyanate was explored. Reactions of (MBMP)Ln(C5H5)(THF)(2) with a molar equiv. of water in THF at -78 degrees C afforded the bis(phenolate) lanthanide hydroxides as dimers [(MBMP)Ln(mu-OH)(THF)(2)}(2)] [Ln = Nd (1), Yb (2)] in high yields. Complexes 1 and 2 reacted with phenyl isocyanate in THF, after workup, to give the desired O-H addition products, [(MBMP)Ln(mu-eta(1):eta(2)-O2CNHPh)(THF)(2)](2) [Ln = Nd (3), Yb (4)] in excellent isolated yields. These complexes were well characterized, and the molecular structures of complexes 2 to 4 were determined by X-ray crystallography. The ytterbium atom in complex 2 is coordinated to six oxygen atoms to form a distorted octahedral geometry, whereas each metal center in complexes 3 and 4 is seven-coordinated, and the coordination geometry can be best described as a distorted pentagonal bipyramid. (C) 2008 Elsevier Ltd. All rights reserved.