The electronic structure of tetraphosphorus trisulphide

Abstract

The electronic structure of P 4 S 3 has been investigated by the Xα scattered wave (XαSW) method as well as by the extended Hückel (EH) and complete neglect of differential overlap (CNDO) molecular orbital methods. The XαSW method gives a particularly good account of the ionization energies determined by HeI photoelectron spectroscopy. The valence shell levels fall into two groups. Those of lower energy are for the most part multicentre orbitals having high s character. The upper occupied levels are non-bonding or weakly bonding, and have a large p component. Contour plots of wave functions and charge distributions emphasize the importance of 'bent bonding' associated with electron density outside the framework of the cage structure, and of multicentre density inside the cage structure. These calculations provide a basis for understanding the relationship between the chemical properties of P 4 S 3 and its electronic structure.