Tetrasilabutadienes synthesis

Thus, in 1997 Weidenbruch and coworkers have reported the synthesis and isolation of the first stable conjugated Si-Si double-bond compound, i.e. hexatipyltetrasilabuta-1,3-diene 9479. Tetrasilabutadiene 94 was prepared through a rather unique synthetic route starting from the corresponding tetraaryl-substituted disilene 95 via the mono-lithiated disilene 96 as shown in Scheme 35. 

Molecules with endocyclic Si=Si double bonds, like the tetrasilabutadiene 139, have also only recently become accessible and their chemistry has not yet been reviewed. In the less than four years since 1996 two three-membered, two four-membered and three five-membered ring compounds containing an Si=Si double bond have been prepared and, in most cases, their structures have been characterized by X-ray crystallography. Although two synthetic routes dominate in the synthesis of acyclic disilenes, the cyclic disilenes have mostly been prepared by the special methods summarized below. 

The recent synthesis of tetrasilabutadiene 1 [1] and of tetrasilacyclobutene 2 [2, 3] in the groups of Weidenbruch and Kira, respectively, has renewed the interest in Si4H6 isomers, their properties and their interconversions. The bicyclic compound 3 [4] has attracted considerable interest in the past, both theoretically and experimentally, due to the possibility of bond-stretching isomers [5,6]. More recently the groups of Kira [7] and Sekiguchi [8] were also succesful in the synthesis of silyl-substituted trisilacyclopropenes 4. 

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