Understanding the electronic structure, reactivity, and hydrogen bonding for a 1,2-diphosphonium dication

Area of Science:

• Chemical Crystallography
• Quantum Chemistry
• Materials Science

Background:

• Understanding the nature of chemical bonds is fundamental in chemistry.
• The P-P bond in diphosphonium compounds presents unique challenges due to potential electrostatic repulsion.
• Previous studies have explored similar structures, but a detailed charge density analysis is often lacking.

Purpose of the Study:

• To experimentally determine the charge density of hexamethyldiphosphonium ditriflate.
• To compare experimental findings with theoretical calculations for gas-phase and crystalline structures.
• To elucidate the nature of the P-P bond and its influence on chemical reactivity and electronic structure.

Main Methods:

• Low-temperature high-resolution X-ray diffraction for experimental charge density determination.
• Theoretical calculations for isolated gas-phase compound analysis.
• Topological analysis of electron density and electrostatic potentials.

Main Results:

• Experimental and theoretical charge densities confirm the covalent nature of the P-P bond.
• Positive charges localize on phosphorus atoms, indicating bond formation despite repulsion.
• Topological properties and electrostatic potentials provide insights into chemical reactivity.
• Analysis of related species (P2Me4, P2Me5(+), P2Me6(+2)) shows the progression of the P-P bond.

Conclusions:

• The P-P bond in hexamethyldiphosphonium ditriflate is covalent, characterized by specific charge distributions.
• Electronic structure and chemical reactivity are significantly influenced by bonding and intermolecular interactions.
• Weak hydrogen bonding plays a role in the electronic structure of these diphosphonium dications.