The d(0), d(1) and d(2) Configurations in Known and Unknown Tetrathiometal Compounds MS(4)(n)()(-) M = Mo, Tc, Ru; W, Re, Os. A Quantum Chemical Study.

The known tetrathiometalates MoS(4)(2)(-)(/3)(-), WS(4)(2)(-)(/3)(-), ReS(4)(-)(/2)(-)(/3)(-), and the unknown species TcS(4)(-)(/2)(-), RuS(4)(0/)(-), and OsS(4)(0/)(-)(/2)(-) were calculated using ab initio and DFT methods. The one-electron reduced species with d(1) configuration were shown to exhibit a slight Jahn-Teller distortion (T(d)() --> D(2)(d)()); the largest corresponding stabilization energy was obtained for MoS(4)(3)(-) with -4.17 kcal/mol. Trends in vacuum bonding energies involve a destabilization on going from 5d(n)() to 4d(n)() systems and on reduction from d(0) to d(1) species, with the exception of Ru and Os complexes where the d(1) configurations are more stable than the d(0) forms. The d(2) species ReS(4)(3)(-) and OsS(4)(2)(-) 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 the neutral RuS(4) and OsS(4) and highest for the dianions MoS(4)(2)(-) and WS(4)(2)(-). The DFT approach supported by correlated ab initio calculations describes the main features of the electronic spectra of the d(0) complexes. For the experimentally best accessible ReS(4)(n)()(-) system the absorption energies and stretching frequencies were well reproduced, and the related but hitherto unknown OsS(4)(-) ion is predicted to be a fairly stable paramagnetic species.