For carbenes with the same neighboring atoms (α-N,N), increasing the Y-Ccarbene-Y angle along the series A < C < D < E < F (Table ) leads to a decrease in JC-H, suggesting an increase in σ- As seen previously, the substituents play only a minor influence on the 1 JC-H value, contrary to what is observed for HEP. Nevertheless, for a specific class of NHC, as observed for pyrazolin-3-ylidene (H), a correlation is roughly obtained between