Hetero-Polar Sextuple Bond: A Relativistic Quantum Chemical Study

Area of Science:

• Quantum Chemistry
• Materials Science

Background:

• The maximum number of covalent bonds between two atoms can exceed four, with six being the theoretical maximum.
• While homopolar sextuple bonds (e.g., in Mo2 and W2) are known, achieving such high bond orders in heteropolar (polar) diatomic molecules has been a significant challenge.

Purpose of the Study:

• To investigate the possibility of forming a sextuple bond in a heteropolar diatomic molecule.
• To explore the electronic structure and bonding characteristics of the Rhodium-Scandium (RhSc) diatomic molecule.

Main Methods:

• Relativistic quantum chemical calculations were employed to model the RhSc system.
• Analysis of electron sharing and dative bonding contributions was performed.

Main Results:

• The study provides evidence for the existence of a sextuple bond in the RhSc heterodiagonal molecule.
• The bonding in RhSc consists of three normal electron-sharing covalent bonds and three dative covalent bonds.

Conclusions:

• The findings demonstrate that sextuple bonds can exist in polar diatomic molecules, challenging previous assumptions.
• This research opens new avenues for exploring and designing molecules with exceptionally high bond orders.