Primary cyclopentadienylphosphines and cyclopentadienylarsines have been prepared by reduction of the corresponding dichloro derivatives and characterized by NMR and photoelectron spectroscopy and mass spectrometry. Their fluxional behavior has been established by both low-temperature NMR experiments and theoretical (DFT) calculations. The structure and the possible pathways to the circumambulatory rearrangement have been determined by quantum chemical computations. The high rate of the 1,2-rearrangement which favors retention of configuration at the migrating atom is explained by a low barrier due to the aromaticity of the transition states. The NMR and photoelectron spectra were assigned by making use of HF-GIAO and OVGF computations, respectively. The observed splitting of the photoelectron bands, compared to those of cyclopentadiene and EX 3 (E ) P, As; X ) H, Cl), was attributed to a hyperconjugative interaction between the cyclopentadienyl ring and the carbon-element bond.

The rotational spectrum of vinylstibine was recorded by pulsed-nozzle microwave Fourier transform spectroscopy between 5 and 40 GHz. andC13CH121SbH 2 isotopic species were observed in natural abundance and frequencies of the lines were Ðtted H 2 C13CH123SbH 2 to the Hamiltonian of Watson (A reduction, Ir representation). Rotational and quartic centrifugal distortion constants and also quadrupole tensor elements and spinÈrotation constants were derived for each isotopic species. An substitution distance for the CÈSb bond length was calculated as r s r s(ChSb) \ 2.13(3) A .

No abstract

No abstract