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Updated: Jan 13, 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
Photochemical Tungsten-Carbon Bond Cleavage in Bicyclic Tungstacyclopentanes
René Riedel1, Robert J Dillon1,2, Logan Trowbridge1
1Department of Chemistry, University of California, Riverside, California 92507, United States.
Abstract:
W(NCPh3)(OSiPh3)2(C7H12) (1) and W(NAd)(OSiPh3)2(C7H12) (2) undergo photochemical α-hydrogen abstraction to form alkylidenes. Transient absorption studies suggest that fast W-C homolysis precedes thermal α-hydrogen abstraction. Radical trapping experiments in the presence of 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) support formation of an alkyl radical in these reactions. DFT calculations of models of 1 and 2 are also consistent with formation of W(V)-alkyl-radical intermediates that ultimately abstract an α-hydrogen to form the alkylidene. This study provides evidence for W-C bond cleavage in reactions that convert catalytically inactive d0 tungstacyclopentanes into metathesis-active alkylidenes.
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