THE STUDY OF ELECTRONIC-STRUCTURE OF CUBANE CLUSTER COMPOUNDS RE4-XMOXS4TE4 BY X-RAY-EMISSION AND X-RAY ELECTRON-SPECTROSCOPY

The electronic structure of the polymeric cubane cluster compounds, Re 4S4Te4 and related phases, has been studied by X-ray emission and X-ra y electron spectroscopy. Calculations;of the electronic structure of t he cubane cluster fragment [Re4S4](8+) by EHMO technique are carried o ut and the binding energy of MO and contributions of AO into MO for [R e4S4](8+) fragment are found. It is shown that in the [Re4S4]8+ core t he upper orbitals of-symmetry t(2), e, and a(1) correspond to M-M bond s but there is a considerable contribution of p-orbitals of sulphur in the orbitals of symmetry a(1); the orbitals e, t(1), t(2) and a(1), t (2) correspond to M-S bonds. Results obtained for [Re4S4](8+) were com pared with analogons data for [MO4S4](4+); it is established that in b oth these cubane cluster fragments the energy levels of analogous MO a nd the contributions of sulphur and metal atoms are different. Replace ment of the rhenium atoms in the [Re4-xMO4S4] cluster core by molybden um changes the energy position and relative intensities of the peaks i n both sulphur and tellurium spectra that indicates the change of natu re of the bonds in the fragment [Re4-xMo4S4] and of the bonds of this fragment with the [Te-4] tetrahedrons.