Syntheses of New {Tetrakis(1-pyrazolyl)borato}samarium(III) Complexes and Their Temperature-Dependent Exchange Motions of All Pyrazolyl Groups

As the first unambiguous syntheses and characterization of the {tetrakis(1-pyrazolyl)borato}lanthanide(III) complexes, stable eight-coordinate (β-ketoenolato)samariums [Sm{η3-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 equivalence of coordinated and uncoordinated pyrazolyl groups at high temperatures.