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Updated: Jul 16, 2025

Accessing Valuable Ligand Supports for Transition Metals: A Modified, Intermediate Scale Preparation of 1,2,3,4,5-Pentamethylcyclopentadiene
Published on: March 20, 2017
Synthesis, Structure, and Reactivity of Magnesium Pentalenides
Hugh J Sanderson1, Gabriele Kociok-Köhn2, Ulrich Hintermair1,3
1Department of Chemistry, University of Bath, Claverton Down, Bath BA2 7AY, U.K.
Abstract:
The first magnesium pentalenide complexes have been synthesized via deprotonative metalation of 1,3,4,6-tetraphenyldihydropentalene (PhPnH) with magnesium alkyls. Both the nature of the metalating agent and the reaction solvent influenced the structure of the resulting complexes, and an equilibrium between Mg[PhPn] and [BuMg][PhPn] was found to exist and investigated by NMR, XRD, and UV-vis spectroscopic techniques. Studies on the reactivity of Mg[PhPn] with water, methyl iodide, and trimethylsilylchloride revealed that the [PhPn] unit undergoes electrophilic addition at 1,5-positions instead of 1,4-positions known for the unsubstituted pentalenide, Pn, highlighting the electronic influence of the four aryl substituents on the pentalenide core. The ratio of syn/anti addition was found to be dependent on the size of the incoming electrophile, with methylation yielding a 60:40 mixture, while silylation yielded exclusively the anti-isomer.
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