THE CHEMICAL BONDING OF Re3Cl9 AND Re3Cl92- REVEALED BY THE ADAPTIVE NATURAL DENSITY PARTITIONING ANALYSES

Chemical bonding of neutral rhenium trichloride Re3Cl9 and doubly charged Re3Cl92- has been brought into question in the current work. Despite recently reported propositions of pi-aromaticity of neutral Re3Cl9 based on negative nuclear independent chemical shift (NICS) values([1,2]) to the contrary, it is shown to be a purely classical chemical molecule, according to the results of the recently developed Adaptive Natural Density Partitioning (AdNDP) analysis.([3-5]) The formation of three consecutive double bonds in a triatomic cycle formed by rhenium atoms that was initially predicted by Cotton et al.([6-8]) is confirmed. The chemical bonding picture changes dramatically upon addition of two excess electrons to Re3Cl9. The rhenium atoms of the resulting doubly charged cluster are shown to be held together via three single Re-Re sigma-bonds, three Re-Cl-Re sigma-bonds, and a totally delocalized pi-bond based on valence d atomic orbitals (d-AO) of rhenium atoms with minor contributions coming from the density associated with six apical chlorine atoms, which makes Re3Cl92- pi-aromatic.