Comparison of bis(alkylthio)carbenes by density functional and Second‐order Møller–Plesset perturbation theory

Thermodynamic parameters (including steric effects) of 15 new pairs of singlet and triplet bis(alkylthio)carbenes, R 1 − S 1 −C ¨ −S 2 − R 2 , ( 1 R1 , R2 and 3 R1 , R2 , respectively), are compared and contrasted by B3LYP and MP2/AUG‐CC‐PVTZ; where R 1 (or R 2 ) = H, Me, Et, i ‐Pr, and t ‐Bu. Among the 30 carbenes scrutinized, the lowest nucleophilicity ( N ) and the highest electrophilicity ( ω ) are displayed by singlet 1 H , H . In contract, triplet 3 i‐ Pr , t ‐Bu exhibits the highest N , while the lowest ω is demonstrated by 3 Me , Et . The maximum and minimum carbenic bond angles (S 1 −C ¨ −S 2 ) are displayed by singlets 1 H , H and 1 Me , Me and triplets 3 t ‐Bu , t ‐Bu and 3 H , Et , respectively. The highest and lowest stability (∆ E s‐t ) are exhibited by 1 Me , t ‐Bu and 1 H , H , respectively. The former may be stabilized primarily through lone pair donations from their sulfur atom into the empty p π carbenic orbital, plus the formation of a five‐membered ring between hydrogen of methyl groups and the carbenic carbons. The highest and lowest band gaps (∆E H‐L ) are exhibited by 3 H , H and 1 t ‐Bu , t ‐Bu , respectively. The highest and lowest chemical potentials ( μ ) are exhibited by 3 Et , i‐ Pr and 1 H , H , respectively. Moreover, second‐order Møller–Plesset perturbation theory (MP2) provided a better discrimination between the scrutinized carbenes than density functional theory (DFT).