Comment on "Evaluation of Y- versus linear-delocalization and the role of charge alternation in trimethylenemethane dianion and butadiene dianions"

The conclusions on the relative stabilities of linear and Y-conjugated forms of the C₄H^2-₆ dianion by Agranat, Radhakrishnan, Herndon, and Skancke are based on calculated structures which are higher-order saddle points and not minima on the potential energy hypersurface. The energy minimum conformations clearly show that the trimethylenemethane dianion is more stable than the linear forms because of a more favorable charge distribution.