SYNTHESIS AND PROPERTIES OF TETRAPHENYLTRIAFULVENE

Article abstract of DOI:10.1016/S0040-4020(01)97689-6

The reaction of the 1,2-diphenylcyclo propenium ion (5) with benzhydrylmagnesium bromide exclusively affords 1,2-diphenyl-3-benzhydrylcyclo propene (4), though the reaction of 5 with benzhydryllithium in the presence of lithium chloride yields no cyclopropene 4 but 1,3-diphenyl-3-benzhydryl-cyclopropene (6) via the intermediate formation of 1,2-diphenyl-3-chlorocyclopropene (7).The hydride abstraction from the cyclopropene 4 followed by deprotonation gives tetraphenyltriafulvene (2) as dark red crystals.The 13C NMR spectrum, as well as a bathochromic shift of the longest-wavelength absorption in the electronic spectrum with decrease in solvent polarity, indicates a considerable contribution of the dipolar structure at the ground state of 2.The cyclic voltammetry on 2 reveals that 2 can be readily oxidized to a stable cation radical and a less stable dication.The cation radical was also generated by chemical oxidation with silver tetrafluoroborate or antimony pentafluoride, and was investigated by ESR spectroscopy.