Sigma-pi Interactions In Alkynyltin(iv) Compounds Studied By Uv Photoelectron-spectroscopy and Pseudopotential Abinitio Calculations

Joint analysis of gas-phase UV photoelectron spectra (UPS) and pseudopotential “ab initio” calculations was used to gain insight into the nature and the mechanism of the interactions between the πc=c and σSn-c orbitals in a series of alkyltin acetylides. The results clearly indicate that the σ /π conjugation is quite extensive along the whole series and that the mechanism is critically controlled by the substituents at both the tin and the alkynyl moiety. Good agreement between the experimental ionization energies and the eigenvalues calculated by the pseudopotential “ab initio” model indicates that this method is suitable for a nonempirical description of the electronic structure of a molecule containing heavy atoms. © 1985, American Chemical Society. All rights reserved.