Determining the Ligand Properties of N-Heterocyclic Carbenes from Se-77 NMR Parameters

作者：Verlinden Kathrin; Buhl Hannes; Frank Walter; Ganter Christian^*

来源：European Journal of Inorganic Chemistry, 2015, 2015(14): 2416-2425.

DOI：10.1002/ejic.201500174

• Nitrogen heterocycles
• Carbenes
• Ligand properties
• Rhodium
• Selenium
• NMR spectroscopy

The (1)J(CSe) coupling constants for a range of NHC-selenium adducts have been measured and used to establish a correlation with the sigma-donor strength of the respective carbenes. For the subclass of amido-carbenes, the (1)J(CSe) values revealed a high donor capacity, very much in contrast to what the DFT-calculated HOMO energies suggest. The (1)J(CH) coupling constants for the C-2 atoms in azolium-type NHC precursors were more readily obtained and show the same trend as the (1)J(CSe) coupling constants. In addition, the use of Se-77 chemical shifts to determine -acidity has been extended to a broader range of derivatives, namely 1Se-22Se. The superior resolution of the (Se-77) method in comparison with the Tolman electronic parameters derived from IR spectroscopy is demonstrated for the caffeine-derived bis-carbene 19.

• 出版日期2015-5