Determination of the Central Bond Length in Hexaarylethanes by Nutation NMR Spectroscopy

Abstract

The lengths of the central bonds, rc, in [α,α'−13C2]hexakis(2,6-di-tert-butyl-4-biphenylyl)ethane (1) and [α,α'−13C2]hexakis(3,5-di-tert-butylphenyl)ethane (2) have been determined by nutation NMR spectroscopy. The dipolar spectra obtained by this method were compared with computed spectra in which the central bond length was the only adjustable parameter. Best fits of the experimental and computed spectra were found to correspond to a rc value between 1.64 and 1.65 Å for both compounds. These results are in excellent agreement with the X-ray value of rc in 2 and provide the first direct experimental evidence that the reported4 X-ray value of rc in 1 is grossly in error. © 1988, American Chemical Society. All rights reserved.