Understanding the Electronic Structure, Reactivity, and Hydrogen Bonding for a 1,2-Diphosphonium Dication

The experimental charge density for hexamethyldiphosphonium ditriflate has been determined from low-temperature high-resolution X-ray diffraction data. These results have been compared with theoretically
calculated values for the isolated gas-phase compound. Analysis of the topological and atomic basin properties
has provided insight into the exact nature of the P−P bond in both the crystalline and the gas-phase structures.
The ρb(r) and ∇2ρb(r) values highlight the covalent nature of the P−P bond, while the atomic charges indicate
a localization of the positive charges on the two phosphorus atoms. This seems to indicate that a covalent
bond is formed despite a strong electrostatic repulsion between these two heteroatoms. The topological
properties and electrostatic potentials have also been shown to provide significant insight into the chemical
reactivity of the title compound. A topological analysis of P2Me4, P2Me5+, and P2Me6+2 species has provided
information about the progression of the P−P bond in the synthesis of the title compound. An investigation
of the different hydrogen-bonding networks present in the crystalline and gas-phase structures, along with
their affect on the electronic structure of the title compound has also been investigated. This has all led to
significant new insight into the electronic structure, reactivity, and weak hydrogen bonding in prototypical
1,2-diphosphonium dications.