Unexpected - orbital covalent interaction between the non--block main-group metal tellurium and fluorine at high pressure.

As a 5-block main-group metal, tellurium generally loses its outermost electrons and forms ionic compounds upon encountering more electronegative elements under ambient conditions. Here, we report an unexpected orbital covalent interaction between the 5-block metal tellurium and the most electronegative element F at high pressure. In tellurium fluorides, the strong fluorine ligand field affects the effective nuclear charge of the metal atom and then affects the valence orbital energies of the central tellurium atom, incorporating unoccupied 5 orbitals of tellurium into the valence orbitals and interacting strongly with the valence orbitals of F atoms under high pressure. An electronic structure analysis of tellurium fluorides reveals the existence of strong covalent interactions in the Te-F system. This study is extremely valuable for advancing our understanding of chemical bonding and high-pressure main-group chemistry.