Comparison of bis(alkylthio)carbenes by density functional and Second-order Moller-Plesset perturbation theory

Thermodynamic parameters (including steric effects) of 15 new pairs of singlet and triplet bis(alkylthio)carbenes, R-1- S-1-C-center dot-S-2- R-2, (1(R1,R2)and3(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, andt-Bu. Among the 30 carbenes scrutinized, the lowest nucleophilicity (N) and the highest electrophilicity (omega) are displayed by singlet1(H,H). In contract, triplet3(i-Pr,t-Bu)exhibits the highestN, while the lowest omega is demonstrated by3(Me,Et). The maximum and minimum carbenic bond angles (S-1-C-center dot-S-2) are displayed by singlets1(H,H)and1(Me,Me)and triplets3(t-Bu,t-Bu)and3(H,Et), respectively. The highest and lowest stability ( increment Es-t) are exhibited by1(Me,t-Bu)and1(H,H), respectively. The former may be stabilized primarily through lone pair donations from their sulfur atom into the empty p(pi)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 ( increment EH-L) are exhibited by3(H,H)and1(t-Bu,t-Bu), respectively. The highest and lowest chemical potentials (mu) are exhibited by3(Et,i-Pr)and1(H,H), respectively. Moreover, second-order Moller-Plesset perturbation theory (MP2) provided a better discrimination between the scrutinized carbenes than density functional theory (DFT).