As the first unambiguous syntheses and characterization of the tetrakis(1-pyrazolyl)borato}lanthanide(III) complexes, stable eight-coordinate (β-ketoenolato)samariums [Smη3-B(pz)4}2(β-ketoenolato)] (pz = 1-pyrazolyl group) were prepared, and novel stereochemically non-rigid temperature-dependent motions of the B(pz)4 ligands were observed on their solution-state 1H-NMR spectra, showing the spectroscopic