A BPtS cluster: a planar tetracoordinate boron system with three charges all at their global energy minima

Although many planar hypercoordinate boron clusters of B n and their expanded derivatives widely exist with specific charges on their wheel-shaped ground-state structures, the planar tetracoordinate boron (ptB) as the sole central atom is seldom reported. To the best of our knowledge, there has been no report of one system that has three charges all possessing planar tetracoordination. Here, we identified an entirely ptB cluster of BPt 4 S 4 , where the peripheral sulfur atoms are the key to maintaining the whole skeleton. The most remarkable feature is that the BPt 4 S 4 n ( n = 2−, 1−, 0) samples are all confirmed to be entirely planar geometries at their global energy minima (GEM) through the CALYPSO global search method. The molecular orbital analysis of the lowest energy anion of BPt 4 S 4 − suggests that it has double (2π and 6σ) aromaticity. Therefore, the ptB-containing BPt 4 S 4 − cluster is expected to be captured in experiment. The monoanion state of BPt 4 S 4 − possesses the lowest energy among the three oxidation states with planar tetracoordinate boron.