state and in solution. Novel four-membered-ring compounds, such as Tbt(Mes)Si(μ-S)2PnBbt and [Tbt(Mes)Si(μ-E)(μ-E′)MLn] [E, E′ = O, S, Se; Pn = Sb, Bi; Bbt = 2,6-bis[bis(trimethylsilyl)methyl]-4-[tris(trimethylsilyl)methyl]phenyl; MLn = Pd(PPh3)2, Pt(PPh3)2, Ru(η6-benzene)] were synthesized by utilizing the silanedichalcogenols as key building blocks. The molecular structures of these newly isolated