Planar Tetracoordinate Hydrogen: Pushing the Limit of Multicentre Bonding

Among the list of planar tetracoordinate atoms, the smallest element hydrogen is missing. No experimental and theoretical evidence have ever been put forwarded. Herein, we introduce the first planar tetracoordinate hydrogen atom (ptH) in the global minimum geometry of In4H+ cluster. Bonding analysis indicates that the central hydrogen atom is acting like a proton and significant charge transfer from the surrounding In4 framework results in a negative charge of the central hydrogen atom. The proposed global minimum geometry possesses sigma-aromaticity and the central hydrogen atom forms unusual multicentre bond with more than three centres. Planar tetracoordinate hydrogen atom has been predicted for the first time in the global minimum D4h geometry of In4H+ cluster.image

Automated summary

In this study, the first planar tetracoordinate hydrogen atom (ptH) was discovered in the global minimum geometry of an In4H+ cluster. The ptH is negatively charged and forms multicentre bonds.