Donor Strength Determination of Anionic Ligands.

Area of Science:

• Organometallic Chemistry
• Coordination Chemistry
• Spectroscopy

Background:

• N-heterocyclic carbenes (NHCs) are important ligands in organometallic chemistry.
• Gold(I) complexes with NHC ligands exhibit diverse applications.
• Understanding the electronic properties of ligands is crucial for catalyst design.

Purpose of the Study:

• To synthesize and characterize new gold(I) NHC complexes.
• To systematically compare and rank the donating abilities of various anionic ligands.
• To establish a reliable method for assessing ligand donor strength in gold complexes.

Main Methods:

• Synthesis of 14 new gold(I) NHC complexes of the type [AuX(iPr2-bimy)].
• Full characterization of the synthesized complexes.
• ¹³C NMR spectroscopy to measure carbene chemical shifts.

Main Results:

• The ¹³C NMR chemical shift of the ^iPr2-bimy ligand was found to be highly sensitive to the nature of the anionic ligand (X).
• A systematic ranking of 34 anionic X-type donors was established based on their donating abilities.
• A broad range (Δδ > 37 ppm) in carbene chemical shifts was observed, reflecting significant differences in donor strengths.

Conclusions:

• The study provides a valuable method for quantifying and comparing the electronic donating properties of anionic ligands in gold(I) NHC complexes.
• The findings contribute to a deeper understanding of structure-activity relationships in gold catalysis.
• The developed ranking system can aid in the rational design of new gold catalysts with tailored electronic properties.