The Si-Si effect on ionization of β-disilanyl sulfides and selenides

The ionization energies of conformationally constrained, newly synthesized β-disilanyl sulfides and selenides were determined by photoelectron spectroscopy. These ionization energies reflect substantial (0.53-0.75 eV) orbital destabilizations. The basis for these destabilizations was investigated by theoretical calculations, which reveal geometry-dependent interaction between sulfur or selenium lone pair orbitals and σ-orbitals, especially Si-Si σ-orbitals. These results presage facile redox chemistry for these compounds and significantly extend the concept of σ-stabilization of electron-deficient centers.