Synthesis and Studies of the Ln-N Bond Insertion of Methylcyclopentadienyl Lanthanide Pyrazolates

Abstract

Reaction of (C₅H₄Me)₃Ln with two equivalents of 3,5-dimethylpyrazole (HPzMe₂) in THF at room temperature yielded complexes [(C₅H₄Me)Ln(PzMe₂)₂]₂ [Ln = Sm (1), Tb (2)]. Complexes (1) and (2) react with dimethylsilicone grease to give the insertion products [(C₅H₄Me)Ln(PzMe₂)(OSiMe₂PzMe₂)]₂ [Ln = Sm (3), Tb (4)]. The results show that the dimethylsilanone insertion only occurs for the bridging Ln-N bond of methylcyclopentadienyllanthanide pyrazolates. All complexes were characterized by elemental analyses, IR spectra and mass spectra. X-ray diffraction reveals complex (4) to be a centrosymmetric dimer in which each terbium atom is coordinated by one methylcyclopentadienyl group, two bridging oxygen atoms and three nitrogen atoms, two from the chelating PzMe₂ ligand and one from the bridging dimethylpyrazolyl group to form a distorted octahedron. The average Tb-C and Tb-O distances are 2.700(4) and 2.318(3) Å, respectively. The Tb-N distances are 2.331(4), 2.390(4) and 2 464(4) Å, respectively.