S. El Chaouch et al., Synthesis and characterization of primary cyclopentadienylphosphines and cyclopentadienylarsines, ORGANOMETAL, 20(25), 2001, pp. 5405-5412
Primary cyclopentadienylphosphines and cyclopentadienylarsines have been pr
epared by reduction of the corresponding dichloro derivatives and character
ized by NMR and photoelectron spectroscopy and mass spectrometry. Their flu
xional behavior has been established by both low-temperature NMR experiment
s and theoretical (DFT) calculations. The structure and the possible pathwa
ys to the circumambulatory rearrangement have been determined by quantum ch
emical computations. The high rate of the 1,2-rearrangement which favors re
tention of configuration at the migrating atom is explained by a low barrie
r due to the aromaticity of the transition states. The NMR and photoelectro
n spectra were assigned by making use of HF-GIAO and OVGF computations, res
pectively. The observed splitting of the photoelectron bands, compared to t
hose of cyclopentadiene and EX3 (E = P, As; X = H, Cl), was attributed to a
hyperconjugative interaction between the cyclopentadienyl ring and the car
bon-element bond.