Synthesis, reactivity and structural characterization of lanthanide hydroxides stabilized by a carbon-bridged bis(phenolate) ligand

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 °C afforded the bis(phenolate) lanthanide hydroxides as dimers [{(MBMP)Ln(μ-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(μ-η1:η2-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.

Controlled hydrolysis of the carbon-bridged bis(phenolate) lanthanide cyclopentadienyl complexes (MBMP)Ln(C5H5)(THF)2 in THF at −78 °C afforded the corresponding lanthanide hydroxides as dimers [{(MBMP)Ln(μ-OH)(THF)2}2] (Ln = Nd (1), Yb (2)), which reacted with phenyl isocynate in THF to give the desired O–H addition products, [(MBMP)Ln(μ-η1:η2-O2CNHPh)(THF)2]2 (Ln = Nd (3), Yb (4)) in excellent isolated yields.Figure optionsDownload as PowerPoint slide