DFT STUDY OF NEWP-HETEROCYCLIC SILYLENES

Abstract

Following our quest for new divalents, we report the synthesis of P-heterocyclic silylenes (PHSis) by adding from one to four phosphorous atoms to saturated cyclopentasilylene (1) and unsaturated cyclopentasilylene-3-ene (1′) resulting in respective PHSis (2-10 and 2′-10′, respectively) and their study at the B3LYP/6-311++G** level of theory. Stabilities of 1-10 and 1′-10′ assumed as the energy gaps between the singlet (s) and triplet (t) states (ΔEs-t) are compared and contrasted. With increasing number of phosphorous atoms, singlet-triplet energy gap (ΔEs-t), nucleophilicity (N), electrophilicity (ω), chemical potential (μ), band gap (ΔEH-L), positive natural bond orbital (NBO) charge on the Si atom, and reactivity decrease. Changes in the hydrogenation enthalpy (ΔHHyd) of 1-10 and 1′-10′ show negative values indicating that the formation of hydrogenated divalent silylenes is exothermic (1H-10H and 1H′-10H′, respectively). The positive overall change in the Gibbs free energy of reaction (ΔGover for the conversion of 1′-10′ to 1-10, respectively) confirms that every 1′-10′ is more stable than its corresponding 1-10.