Synthesis and characterization of tris(3,5-dimethylpyrazolyl)borate lanthanide halide and benzyl complexes: a study across early lanthanides.

The reaction of LnX3(THF)n (n = 0, 2 and X = Cl, Br) with two equivalents of KTp* formed Tp*2LnX [Ln = La (1-La), Ce (1-Ce), Pr (1-Pr), Nd (1-Nd, 2-Nd), Sm (1-Sm), Eu (1-Eu), Gd (1-Gd)] in high yields. Treating these species with one equivalent of KCH2Ph afforded either the corresponding benzyl (Ce, Pr, Nd) or the divalent Tp*2Ln(II) (Sm, Eu) derivatives. Although paramagnetic, these complexes were characterized by 1H- and 11B-NMR spectroscopy. Additional characterization of these species was accomplished using electronic absorption spectroscopy, infrared spectroscopy, and X-ray crystallography. The latter study revealed seven- and eight-coordinate lanthanide ions in distorted trigonal bipyramidal and distorted capped octahedral geometries. Computational analyses of these species supported the experimental oxidation states and geometries, and modeled the spectroscopic data well.