“…[2] The ion-molecular S N 2 model has been thoroughly investigated in theory and experiment, starting with the simple six-atom identity reaction (X À + CH 3 Y, X, Y = F, Cl, Br, I). [2a] There are many nucleophiles and leaving groups beyond the basic halogen ones, such as the normal nucleophiles and leaving groups (OH À , SH À , CN À , NH 2 À , PH 2 À , AsH 2 À , SeH À , etc [3] ), the α-nucleophiles [4] (HOO À , H 2 NO À , CH 3 OO À , CH 3 HNO À , HOHN À , etc) and metal anions as nucleophiles [5] M À + CH 3 X (M = Cu, Ag, Au, X = F, Cl, Br, I). S N 2 reactions of different central atoms have also been extensively studied, mainly focusing on second-period elements C, N, O and F, [6] third-period elements Si, [7] P, [8] S [9] and others.…”