Understanding the reactivity of phosphorus pentasulfide with a series of phosphoryl chloride derivatives: Interplay between σ-hole, π-hole and H-bonding interactions

Abstract

The reactivity of phosphorus pentasulfide (P₂S₅) in the presence of a series of phosphoryl chloride derivatives has been investigated using the M06-2X and B3LYP functionals in conjunction with the 6-311 + G(d,p) basis set. Our computations indicate that both the regioselectivity of P₂S₅ and the physical nature of the interaction in P₂S₅ complexes can be rationalized using conceptual DFT reactivity indices, natural bond orbitals (NBO) and symmetry-adapted perturbation theory (SAPT2 + dMP2). The molecular electrostatic potential (MEP) of P₂S₅ exhibits σ- and π-hole regions around the P = S bond: one hole is carried by the S atom and located along the P-S bond, while two others are found at both sides of the P atom. Unlike the P₄S₁₀ dimer whose reaction is obstructed by a huge activation energy, its monomeric form (P₂S₅) successfully yields a product following a reaction path with a low activation energy and involving metastable complex intermediates. The adducts formed along the P = S unit are less stable than those attacking the P = S bond perpendicularly. The process involves the concomitant weakening of the P···S bond of P₂S₅ and reinforcement of the P=O bond, turning P₂S₅ into P₂S₄O.