The Effect of Selenium-Based Ligands on Tungsten Acetylene Complexes

Area of Science:

• Organometallic Chemistry
• Bioinorganic Chemistry
• Coordination Chemistry

Background:

• Tungsten complexes are relevant for modeling enzyme active sites, such as acetylene hydratase.
• Previous theoretical studies suggested selenium substitution could enhance tungsten enzyme activity.
• Understanding ligand effects on tungsten complex reactivity is crucial for bioinorganic modeling.

Purpose of the Study:

• To synthesize and characterize novel bioinspired tungsten acetylene complexes using pyridine-2-selenolato ligands.
• To investigate the influence of selenium ligands on the reactivity and electronic properties of tungsten complexes.
• To compare selenium-based complexes with previously studied sulfur-based analogs in the context of acetylene hydratase modeling.

Main Methods:

• Synthesis of tungsten complexes with pyridine-2-selenolato (PySe) and 6-methyl-pyridine-2-selenolato (6-MePySe) ligands.
• ⁷⁷Se NMR spectroscopy for structural and electronic analysis of the ligands.
• Reactions involving migratory insertion of acetylene, oxidation, and addition of phosphines and alkynes.

Main Results:

• Selective synthesis of tungsten acetylene complexes with PySe and 6-MePySe ligands, demonstrating control over chemoselectivity.
• Characterization of tungsten(IV) and tungsten-carbene/alkylidene complexes through various reactions.
• Comparative analysis revealed negligible structural and electronic differences between selenium- and sulfur-based complexes.

Conclusions:

• The synthesized selenium-based tungsten complexes provide insights into bioinorganic modeling of acetylene hydratase.
• Contrary to theoretical predictions, selenium substitution does not significantly alter the properties compared to sulfur analogs.
• This study highlights the importance of experimental validation in enzyme modeling and suggests limited benefits of sulfur-to-selenium exchange in this system.