The coordination properties of ligands have a major impact on the chemical characteristics of the complexes they form. Their significance is illustrated by their influence on numerous factors, ranging from bond lengths and bond dissociation energies to radical stabilization capability. These coordination properties play a particularly significant role in the catalytic activity of their complexes with transition metals. Therefore, to predict the efficiency of catalysts, ligand descriptors have undergone significant development in recent years. N-heterocyclic carbenes (NHCs) and related C-donor ligands, known to cover a large range of electronic properties, are widely used in homogeneous catalysis. Many experimental descriptors of their bonding capability, such as the Tolman (TEP) , Lever (LEP) and Huynh (HEP) electronic parameters or other indicators based on NMR approach, have been proposed. TEP and LEP (also referred to as ligand electrochemical parameter) both measure the overall donation capability of a ligand L, using respectively the CO stretching frequencies in the IR spectrum of [Ni(CO)3L] or other tetrahedral complexes, and the redox potential of [MCl(COD)L] complexes (M = Rh, Ir). For its part, HEP is based on the C NMR chemical shift of trans-[PdBr2( i Pr2-bimy)L] complexes and primarily measures the σ-donor strength of ligand L. The -acidity of carbenes can be estimated experimentally by measuring the P or Se chemical shift of carbenephosphinidene or carbene-selenium adducts, respectively. The theoretical study of these descriptors has proven to be very useful in establishing the electronic properties of carbenes or confirming the relevance of these descriptors, as illustrated by the work of Gusev and of Nolan and Cavallo. Recently, the magnitude of the JC-H coupling constants in azolium-type NHC precursors (as well as the 1 JC-Se coupling constants in NHC=Se complexes) has been proposed by Ganter as a promising measure of the σ-donation of NHCs. This descriptor is assumed to be strongly related to the s-character of the carbon involved in the C-H bond, with larger 1 JC-H value indicating weaker σ-donor ability. It is particularly attractive for estimating the σ-donation of divalent carbon ligand, as it only requires the C or 1 H NMR spectrum of the readily available NHC precursor azolium salt. On the other hand, the 1 JC-Se coupling constant has been shown to provide valuable information on NHC ligands; however, its measurement is hindered by the low natural abundance of ¹³C and limited Se sensitivity. In this context, the evaluation of 1 JC-H coupling constants has emerged as a more practical alternative for characterizing the σ-donating ability of NHC ligands. Despite recent works showing minimal effect ( 1 JC-H < 0.3 Hz) for concentration and counteranion and modest impact for the solvent nature ( 1 JC-H < 1.5 Hz), there is no systematic study assessing the influence of these parameters on the 1 JC-H value. It is also noted that the 1 JC-H descriptor still faces several issues. Indeed, salts derived from different carbenes, for which chemical evidence indicates different donation capabilities, have been measured with different counterions but still have the same JC-H value. Moreover, the number of available experimental data for this recent descriptor is somewhat limited and does not cover the full diversity of carbene ligands and their derivatives. Finally, no comprehensive comparison with other experimental methods has provided a clear conclusion on its suitability, with only one recent study comparing JC-H and HEP. This study, limited to pyrazole-and indazole-derived NHC, concluded that 1 JC-H and HEP parameters estimate the σ-donor strength similarly, although HEP is more accurate in evaluating subtle differences between molecules. Another commonly used indicator in the literature to assess the σ-donating ability of a carbene is the energy of its highest occupied molecular orbital (HOMO) associated with the lone pair on the carbene carbon. For example, Ganter et al. and Landais et al. reported good linear correlations (R 2 between 0.91 and 0.95) between the HOMO energy and the 1 JC-Se or JC-H coupling constant of selected carbenes, supporting the idea that these descriptors all reflect the σ-donation ability of the carbene. However, it should be noted that these satisfactory correlations required the exclusion of certain compounds, likely indicating a partial disagreement between these descriptors, the reason for which remains unknown.