Activation of CS2 and CS by ML3 complexes.

Area of Science:

• Inorganic Chemistry
• Computational Chemistry
• Materials Science

Background:

• Activating and cleaving multiple bonds in small molecules like carbon disulfide (CS2) and carbon monosulfide (CS) is crucial for chemical synthesis.
• Current experimental methods have limitations in fully cleaving these bonds, particularly both C-S bonds in CS2 and the C-S bond in CS.

Purpose of the Study:

• To computationally determine the most effective neutral ML3 metal complexes for activating and cleaving the C-S bonds in CS2 and CS.
• To elucidate the electronic factors governing the reactivity of ML3 complexes with CS2 and CS.

Main Methods:

• Density functional theory (DFT) calculations were employed to evaluate various ML3 complexes.
• Metal centers studied include M = Mo, Re, W, and Ta, with ligands L = NH2.
• Analysis of molecular orbitals and Mulliken charges was used to understand reaction mechanisms and trends.

Main Results:

• The L3Re/CS2/TaL3 complex is predicted to be highly effective for cleaving both C-S bonds in CS2, with an exothermic reaction (approx. 700 kJ mol-1) and minimal energy barrier.
• The study rationalizes the experimental difficulty in breaking the C-S bond in CS with Mo complexes, identifying it as a strongly endothermic process due to insufficient bond strength compensation.
• ReL3 or a combination of ReL3 and TaL3 are suggested as promising systems for cleaving the C-S bond in CS.

Conclusions:

• Neutral ML3 complexes, particularly those involving Re and Ta, offer a promising pathway for the activation and cleavage of C-S bonds in CS2 and CS.
• Computational insights provide a theoretical foundation for designing future experiments aimed at achieving efficient C-S bond cleavage.
• Understanding the interplay of charge transfer and pi back-donation is key to predicting and optimizing the reactivity of these metal complexes.