Key points are not available for this paper at this time.
The square-like planar tetracoordinate hydrogen global minimum H©K 4 H 4 − can be obtained by introducing one hydrogen anion into the K 4 H 4 ring. One central 5c-2e and four outer 3c-2e σ bonds are responsible for its stability.
Bai et al. (Mon,) studied this question.