Electronic structure of chalcogenols: photoelectron spectroscopic and theoretical studies of tris(trimethylsilyl)silyl chalcogenols

The photoelectron spectra (He I and He II) have been reported for the homol ogous series of tris(trimethylsilyl)silyl chalcogenols (Me3Si)(3)SiEH (E = O, S, Se or Te) and assigned on the basis of predictions from density funct ional theory (DFT) calculations. The DFT calculations indicated that the ch alcogenol HOMO is a pi-type orbital located essentially on the silicon atom s for the lighter chalcogenols, whilst it is located entirely on the chalco gen for selenol and tellurol. DFT was used to predict the H-E-Si bond angle in the idealised species HESi(SiH3)(3). The trends seen, on descending the group, are broadly similar to those obtained for H2E, but are complicated by mixing of silicon orbitals with those of E. The results of these studies are used to rationalise the observed behaviour of some transition metal ch alcogenolate complexes, in particular the facile Te-Si bond cleavage reacti ons which produce terminal tellurides for the early d-block metals.