Strained Ring Compounds Of Silicon And Germanium

Several three- and four-membered rings of silicon and germanium have been obtained by reductive halogen elimination from dihalosilanes or -germanes, respectively. Among these rings hexatert-butylcyclotrisilane and -cyclotrigermane reveal the largest M-M bond lengths within these series of compounds. The chemical behaviour of the cyclotrisilane skeleton is characterized by two paths which can be classified according to the number of Si-Si bond cleavages. In the “dark” one Si-Si bond is cleaved leading to open-chained tri-silanes or to ring insertion products. Photolysis of hexa-tert-butylcyclotrisilane proceeds by cleavage of two Si-Si bonds giving di-tert-butylsilylene and tetra-tert-butyldisilene which can be trapped by various multiply bonded compounds. These trapping reactions lead to several types of small or medium-sized novel silacycles.