THE CHEMICAL BONDING OF Re_3Cl_9 AND Re_3CI_9~(2-) REVEALED BY THE ADAPTIVE NATURAL DENSITY PARTITIONING ANALYSES

摘要

Chemical bonding of neutral rhenium trichloride Re_3Cl_9 and doubly charged Re_3CI_9~(2-) has been brought into question in the current work. Despite recently reported propositions of π-aromaticity of neutral Re_3Cl_9 based on negative nuclear independent chemical shift (NICS) values 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. The formation of three consecutive double bonds in a triatomic cycle formed by rhenium atoms that was initially predicted by Cotton et al. is confirmed. The chemical bonding picture changes dramatically upon addition of two excess electrons to Re_3Cl_9- The rhenium atoms of the resulting doubly charged cluster are shown to be held together via three single Re-Re π-bonds, three Re-Cl-Re σ-bonds, and a totally delocalized re-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 Re_3Cl_9~(2-) π-aromatic.