A quest for triplet silylenes XHSi3 at ab initio and DFT levels (XÂ =Â H, F, Cl and Br)

Four triplet ground state silylenes 3t-X and 4t-X (where X = F and Cl) appear more stable than their corresponding singlet states. This is found through the comparison of singlet-triplet energy splittings for 30 XHSi3 silylenes at seven levels of ab initio and DFT (X = H, F, Cl, and Br).