A quest for triplet silylenes XHSi 3 at ab initio and DFT levels (X = H, F, Cl and Br)

Abstract

Four ground state triplet silylenes are found among 30 possible silylenic XHSi 3 structures (X = H, F, Cl and Br), at seven ab initio and DFT levels including: B3LYP/6-311++G ∗∗, HF/6-311++G ∗∗, MP3/6-311G ∗, MP2/6-311+G ∗∗, MP4(SDTQ)/6-311++G ∗∗, QCISD(T)/6-311++G ∗∗ and CCSD(T)/6-311++G ∗∗. The latter six methods indicate that the triplet states of 3-flouro-1,2,3-trisilapropadienylidene, 1-chloro-1,2,3-trisilapropargylene and 3-chloro-1,2,3-trisilapropargylene are energy minima. These triplets appear more stable than their corresponding singlet states which cannot even exist for showing negative force constants. Also, triplet state of 1-flouro-1,2,3-trisilapropargylene is possibly accessible for being an energy minimum, since its corresponding singlet state is not a real isomer. Some discrepancies are observed between energetic and/or structural results of DFT vs. ab initio data.