Search for Osme Bonds with π Systems as Electron Donors

Area of Science:

• Inorganic Chemistry
• Computational Chemistry
• Quantum Chemistry

Background:

• The Osme bond is theorized as a noncovalent interaction where a Group 8 metal acts as an electron acceptor.
• Understanding these interactions is crucial for predicting chemical reactivity and designing novel materials.

Purpose of the Study:

• To computationally investigate the nature of the Osme bond using Density Functional Theory (DFT).
• To analyze the interaction energies between metal tetroxides (MO4) and various π-electron donors.

Main Methods:

• Density Functional Theory (DFT) calculations utilizing the ωB97XD functional.
• Investigation of MO4 (M = Ru, Os) as Lewis acids interacting with π-donors like acetylene, ethylene, benzene, pyridine, furan, and thiophene.

Main Results:

• Interaction energies ranged from 9.5 to 26.4 kJ/mol.
• Osmium (Os) exhibited stronger interactions than Ruthenium (Ru).
• Interactions with larger π-systems (aromatic rings) were stronger than with smaller ones (ethylene, acetylene).

Conclusions:

• The bonding primarily involves interactions between the π-system and the oxygen atoms of MO4, specifically via π(C-C)→σ*(M-O) electron transfers.
• Back donation from M-O bonds to the π*(CC) antibonding orbitals also contributes.
• Dispersion forces play a significant role, exceeding electrostatic and inductive contributions, questioning the existence of a distinct Osme bond.