DFT study of new P-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 (DEs-t) are compared and contrasted. With increasing number of phosphorous atoms, singlet-triplet energy gap (DEs-t), nucleophilicity (N), electrophilicity (w), chemical potential (m), band gap (DEH-L), positive natural bond orbital (NBO) charge on the Si atom, and reactivity decrease. Changes in the hydrogenation enthalpy (DHHyd) 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 (DGover for the conversion of 1'—10' to 1—10, respectively) confirms that every 1'—10' is more stable than its corresponding 1—10.