Heavy element analogues of bicyclo[1.1.0]butane have attracted much attention as they often exhibit skeletal isomerisations that are not observed for all-carbon bicyclo[1.1.0]butanes. The reaction of a bicyclo[1.1.0]tetrasil-1(3)-ene with CCl₄ at low temperature provided orange crystals of a 1,3-dichlorobicyclo[1.1.0]tetrasilane containing a planar Si₄ ring with a π-type bridgehead Si–Si bond. The equilibrium between the bicyclotetrasilane and an isomer, 1-chloro-2-(chlorosilyl)cyclotrisilene in solution, which is an unprecedented interconversion mode of Si₄R₆ isomers, was identified by NMR spectroscopy and also the formation of its 4-(dimethylamino)pyridine (DMAP) complex.