Cobalt analogues of Roussin's red salt esters: a density functional study

Abstract

Density functional theory calculations on the Co₂(NO)₄(SR)₂ compounds (R = CH₃, CF₃ and C₄H₉) predict butterfly and open isomeric structures with and without a direct Co–Co bond. The open Co₂(NO)₄(SR)₂ structures are favored over the butterfly isomers, in terms of relative energy. Furthermore the open structures are predicted to have approximately twice as large HOMO–LUMO gaps than the butterfly Co₂(NO)₄(SR)₂ isomers. For the related Co₂(CO)₆(SR)₂ species, competing open and butterfly structures with similar HOMO–LUMO gaps were predicted. This could explain why the Co₂(NO)₄(μ-SR)₂ compounds have already been synthesized and why no genuine Co₂(CO)₆(SR)₂ derivatives have yet been reported.