What is the structure of ?

In 1992, Korkin and Schleyer studied in silico the structure of Si 3 H 5 - and concluded that the lowest-energy isomer of this anion has a non-planar Cs structure. More recently, Xiao et al. claimed that a cyclic form is the global minimum structure. However, they did not compare the computed energy with any other structural options. In this manuscript we reexamine the Si 3 H 5 - structure by using a genetic algorithm. We found that two dissimilar structures are candidates to be the global minima structure. One of them was reported by Xiao and coworkers, but a second one, with a coordinatively unsaturated silyl-disilene like structure, is only 0.1 kcal mol−1 less stable.