The d(0), d(1) and d(2) configurations in known and unknown tetrathiometalcompounds MS4n- (M = Mo, Tc, Ru; W, Re, Os). A quantum chemical study

The known tetrathiometalates MoS42-/3-, WS42-/3-, ReS4-/2-/3-, and the unkn own species TcS4-/2-, RuS40/-, and OsS40/-/2- were calculated using ab init io and DFT methods. The one-electron reduced species with d(1) configuratio n were shown to exhibit a slight Jahn-Teller distortion (T-d --> D-2d); the largest corresponding stabilization energy was obtained for MoS43- with -4 .17 kcal/mol. Trends in vacuum bonding energies involve a destabilization o n going from 5d(n) to 4d(n) systems and on reduction froth d(0) to d(1) spe cies, with the exception of Ru and Os complexes where the d(1) configuratio ns are more stable than the d(0) forms. The d(2) species ReS43- and OsS42- have vacuum bonding energies similar to those of d(1) analogues: The metal contribution to the lowest unoccupied MO (e) of d(0) forms is lowest for th e neutral RuS4 and OsS4 and highest for the dianions MoS42- and WS42-. The DFT approach supported by correlated ab initio calculations describes the m ain features of the electronic spectra of the d(0) complexes. For the exper imentally best accessible ReS4n- system the absorption energies and stretch ing frequencies were well reproduced, and the related but hitherto unknown OsS4- ion is predicted to be a fairly stable paramagnetic species.