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Updated: Feb 17, 2026

Accessing Valuable Ligand Supports for Transition Metals: A Modified, Intermediate Scale Preparation of 1,2,3,4,5-Pentamethylcyclopentadiene
Published on: March 20, 2017
Triangles and Squares for a Unique Molecular Crystal Structure: Unsupported Two-Coordinate Lithium Cations and CC
Quentin Dufrois1,2, Jean-Claude Daran1,2, Laure Vendier1,2
1Laboratoire de Chimie de Coordination du CNRS (LCC), 205 route de Narbonne, BP 44099, 31077, Toulouse Cedex 4, France.
Abstract:
Understanding and controlling the aggregation state is germane to alkyllithium chemistry. Lewis base-free alkyllithium compounds normally form tetrahedral tetramers or octahedral hexamers in the solid state with the lithium cations being three-coordinate. We report that the unsupported cyclopropyl derivative 1-(trimethylsilyl)cyclopropyllithium [{μ-c-C(SiMe3 )C2 H4 }Li]4 (1), synthesized by the reduction of 1-(phenylthio)-1-(trimethylsilyl)cyclopropane, crystallizes as a tetramer in the space group I-4 with the two-coordinate lithium atoms forming a square. CC agostic interactions complete the coordination sphere around each lithium. The aggregate is preserved in hydrocarbon solution. Furthermore, CC agostic interactions compete intra- and intermolecularly with Lewis base donation as in the unsaturated dimer of 1-(phenylthio)cyclopropyllithium [Li(thf)2 {μ-c-C(SPh)C2 H4 }2 Li (thf)] (3) which is also fully characterized.
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