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

Abstract

Chemical bonding of neutral rhenium trichloride Re₃Cl₉ and doubly charged has been brought into question in the current work. Despite recently reported propositions of π-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 σ-bonds, three Re-Cl-Re σ-bonds, and a totally delocalized π-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 π-aromatic.

Keywords:

• AdNDP
• chemical bonding
• Re₃Cl₉
• Re₃Cl²⁻ ₉
• transition metal aromaticity

ACKNOWLEDGEMENT

Funding for this research was provided by the National Science Foundation (CHE-0714851). Computer time from the Center for High Performance Computing at Utah State University is gratefully acknowledged. The computational resource, the Uinta cluster supercomputer, was provided through the National Science Foundation under Grant CTS-0321170 with matching funds provided by Utah State University.