Donor Strengths Determination of Pnictogen and Chalcogen Ligands by the Huynh Electronic Parameter and Its Correlation to Sigma Hammett Constants

The suitability and accuracy of the Huynh electronic parameter (HEP) was further tested to reveal remote substituent effects in pyridines, which are located five or six bonds away from the reporter probe. These values show an excellent correlation to Hammett σ‐constants of the respective substituents with coefficients of R (2)=0.9856 (σ (m)) and R (2)=0.9857 (σ (p)). Based on this observation, a methodology for the re‐evaluation of certain Hammett constants with larger uncertainties has been proposed and demonstrated. Moreover, the scope of HEP was extended to various neutral pnictogen and chalcogen donors during which “transphobia effects” were revealed for mixed NHC complexes containing phosphites, arsine and stibine for the first time.