Structural characterization of the bent metallocenes, [C5H3(SiMe3)2]2Sm and [C5H3(CMe3)2]2Ln (Ln = Eu, Sm), and the mono(cyclopentadienyl) tetraphenylborate complex, [C5H3(CMe3)2]Eu(μ-η6:η1-Ph)2BPh2

Abstract

Efforts to generate Ln2+ precursors suitable for reduction to Ln1+ compounds have provided the X-ray crystal structures of Cp″2Sm, 1-Sm, and Cptt2Ln, 2-Ln [Ln = Eu, Sm; Cp″ = C5H3(SiMe3)2; Cptt = C5H3(CMe3)2], allowing direct comparisons of these similar cyclopentadienyl rings in Ln2+ complexes. In the solid state, these complexes exhibit extensive intermolecular interactions. Bridging cyclopentadienyl ligands are found with both types of ligands and the Cp″ ligand engages in silyl-methyl-metal interactions. The compounds display bent metallocene structures with (ring centroid)–Ln–(ring centroid) angles ranging from 110.0° to 147.9°. Complex 2-Eu reacts with [HNEt3][BPh4] to form the mono(cyclopentadienyl) tetraphenylborate complex, (η5-Cptt)Eu(μ-η6:η1-Ph)2BPh2, 3-Eu, in which the Eu2+ ion is coordinated by three carbocyclic ligands in a nearly trigonal planar geometry.