Ligands for dinitrogen fixation at Schrock-type catalysts.

Area of Science:

• Inorganic Chemistry
• Catalysis
• Computational Chemistry

Background:

• Catalytic dinitrogen reduction is crucial for ammonia synthesis but limited by low turnover numbers.
• Degradation of chelate ligands, such as HIPTN(3)N, often hinders catalytic efficiency in Schrock-type complexes.

Purpose of the Study:

• To investigate modifications of the HIPTN(3)N ligand for improved catalytic dinitrogen reduction.
• To explore alternative ligands and their impact on the catalytic performance of molybdenum complexes.
• To establish a structure-reactivity relationship for predicting catalyst feasibility.

Main Methods:

• Density functional theory (DFT) methods were employed to study ligand modifications.
• Full ligand structures were considered without approximations.
• Reaction energies and vibrational frequencies were calculated for various molybdenum complexes.

Main Results:

• Modifications to the HIPTN(3)N ligand showed similar reaction energies to the parent system.
• The [{tris[2-(3-xylyl-imidazol-2-ylidene)ethyl]amine}Mo](N(2)) complex exhibited the most promising catalytic results.
• A direct correlation was found between the N≡N stretching wavenumber and the reaction energy for NH(3)/N(2) exchange.

Conclusions:

• The feasibility of ammonia (NH(3)) to dinitrogen (N(2)) exchange is a critical factor for catalyst potential.
• A derived structure-reactivity relationship allows for the prediction of catalytic activity based on N≡N vibrational frequency.
• This relationship can guide experimental efforts in developing new dinitrogen reduction catalysts.