Structural and variable-temperature NMR studies of 9-diisopropylphosphanylanthracenes and 9,10-bis(diisopropylphosphanyl)anthracenes and their oxidation products

摘要

The diisopropylphosphanyl-substituted anthracenes i-Pr2P(C14H9) (1a), i-Pr2P(C14H8)Br (2a), and (i-Pr2P)(2)(C14H8) (3a) and some of their oxidation products were prepared from 9-bromoanthracene and 9,10-dibromoanthracene, respectively. Low-temperature H-1 NMR spectra of the 9-monophosphanyl-substituted anthracenes la and 2a are in accordance with a staggered conformer, while above room temperature dynamic processes occur. The low-temperature NMR spectrum of the 9,10-diphosphanylanthracene 3a indicates the presence of two different rotational isomers. The rotational barrier for la was determined from variable-temperature H-1 NMR spectra to be 56 kJ mol(-1) (Delta G(298K)). The crystal structure determinations show the solid-state conformers to be consistent with the prevailing conformer at low temperature.