Nucleophilicity and CO2 fixation ability of the ylides of phosphorous, sulfur and nitrogen havebeen assessed using DFT calculations at M06-2X/6-311++G(d,p)//M06-2X/6-31+G(d) level. Nucleophilicityof 54 ylides and their CO2 adducts have been evaluated using a theoretical nucleophilicity index(N) which shows good linear correlation (R2 = 0.87) with Mayr’s experimental nucleophilicity parameter forthe S-ylides. Two key geometrical parameters, condensed Fukui function (fk-) and Gibbs free energy ofreaction (ΔGr) for the ylide-CO2 adducts have also been calculated. In absence of steric effect around theylidic C-atom and any other secondary interaction, binding energy of the CO2-adducts of all the three types ofylides has a good linear correlation with the nucleophilicity. Nucleophilicity of a P-ylide increases whenelectron-donating groups are introduced as substituents on both P and the ylidic C-atom. An electronwithdrawinggroup on the same sites reduces nucleophilicity. Free ylides have higher nucleophilicity thantheir CO2 adducts.
Volume 135, 2023
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