Phenol-Tethered N-Heterocyclic Benzimidazol-2-ylidene Carbene Interactions with the Early Lanthanides

The cyclization of salophan with triethyl orthoformatein the presenceof HBr results in a bisphenol benzimidazolium carbene precursor 1,3-bis(2-hydroxybenzyl)-2H-benzimidazolium bromide (H(3)OBBIm). By reactingH(3)OBBIm in a one-pot synthesis with Ln(N(SiMe3)(2))(3) (Ln = La-Sm excl. Pm) and an excessof KN(SiMe3)(2), the N-heterocycliccarbene (NHC) complexes, [Ln(OBBIm)(2)(N '')][K2THF x ], can be prepared and isolated.These complexes were characterized by single-crystal X-ray diffraction,solution- and solid-state UV-vis-near-infrared spectroscopy,and H-1 NMR. These complexes possess distorted pentagonalbipyramid geometries.