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

Abstract

The photoelectron spectra (He I and He II) have been reported for the homologous series of tris(trimethylsilyl)silyl chalcogenols (Me₃Si)₃SiEH (E = O, S, Se or Te) and assigned on the basis of predictions from density functional theory (DFT) calculations. The DFT calculations indicated that the chalcogenol HOMO is a π-type orbital located essentially on the silicon atoms for the lighter chalcogenols, whilst it is located entirely on the chalcogen 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 chalcogenolate complexes, in particular the facile Te–Si bond cleavage reactions which produce terminal tellurides for the early d-block metals.