BPt4S4 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 BPt4S4, where the peripheral sulfur atoms are the key to maintaining the whole skeleton. The most remarkable feature is that the BPt4S4n (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 BPt4S4- suggests that it has double (2 pi and 6 sigma) aromaticity. Therefore, the ptB-containing BPt4S4- cluster is expected to be captured in experiment.