Property and reactivity of polyselenides and polysulfides: a quantum chemistry study

High-level ab initio and density functional theory were applied to investigate property and reactivity of polyselenides and polysulfides. With CH₃X_nH (X = S or Se) we found that the deprotonation energy (and pK_a) of CH₃Se_nH, ionization potential (IP) of, and CH₃Se_n−H bond dissociation energy (BDE) are lower than those of their sulfur counterparts. For n = 2, IPs and X−H BDEs are exceptionally small. The relative nucleophilicity of $\text{C}{\text{H}}_3{\text{X}}_n^{-}$ vary with substrates. However, CH₃Se_nH are more nucleophilic than CH₃S_nH due to their due to their lower deprotonation energy. The nucleophilicity of selenolates versus thiolates are related to the chemical nature. Selenium is more electrophilic than sulfur.