Donor Strength Determination of Anionic Ligands.

14 new gold(I) NHC complexes of the type [AuX(Pr-bimy)] (Pr-bimy = 1,3-diisopropylbenzimidazolin-2-ylidene) have been prepared and fully characterized. These complexes and their reported analogues were used to systematically compare and rank the donating abilities of overall 34 anionic X-type donors by C NMR spectroscopy. Specifically, the carbene chemical shift of the Pr-bimy ligand was found to be responsive to the ligand X spanning an overall range Δδ > 37 ppm between the strongest and weakest donor in this study.

Anion influences on reactivity and NMR spectroscopic features of NHC precursors.

A series of 16 benzimidazolium salts of the type Pr-bimyHX with various anions X were synthesized and characterized by various spectroscopic and spectrometric methods. Significant anion and solvent effects on the chemical shifts of the C2-H protons were found, which allows for a ranking of the anions in terms of their hydrogen-bond acceptor properties. Stronger acceptors could increase the acidity of their respective salts leading to a faster H/D exchange.