A Dirac molecular orbital study for hexanuclear tungsten cluster structures

Dirac molecular orbital calculations (DSW-Xα) on octahedral hexanuclear tungsten W₆X₈X^2-₆ (X = Cl, Br, I) clusters are reported. The calculated relativistic molecular orbitals clearly indicate that the manifold of closely spaced unoccupied energy levels are mainly metallic in character with contributions from the triply bridging halide ligands, while all the cluster HOMOs are largely centered on the terminal ligands. Upon substitution of the Cl ligands by Br and I, their singlet ground states span different symmetry representations (Γ⁺₆ vs. Γ^-₇). The calculated cluster relativistic charge distributions indicate that these could be formulated as W^-0.05₆Cl^-0.07₈Cl^-0.19₆, W^-0.26₆Br^+0.11₈Br^-0.22₆ and W^-0.48₆I^+0.26₈I^-0.20₆, respectively.