Aluminium Chloride Catalyzed Skeletal Rearrangement of Permethylated Acyclic Polysilanes

Article abstract of DOI:10.1021/ja00406a029

Permethylated linear polysilanes, Me(Me2Si)nMe with n = 4-10 and 12, underwent skeletal rearrangement to give branched isomers in almost quantitative yields when treated with a catalytic amount of aluminium chloride in refluxing benzene.From the linear polysilanes with n = 4, 5, and 6, (Me3Si)3SiMe, (Me3Si)4Si, and (Me3Si)SiSiMe2SiMe3 were obtained, respectively, as single isomer.The polysilanes with n = 7, 8, and 9 were converted into an equilibrium mixture, each consisting of a pair of branched isomers: (Me3Si)SiSiMe32SiMe2SiMe3 (15) and (Me3Si)SiSiMe(SiMe3)2 (16); (Me3Si)3SiSiMe2SiMe(SiMe3)2 (18) and <(Me3Si)3Si>2 (19); and (Me3Si)3SiSiMe2SiMe2SiMe(SiMe3)2 and <(Me3Si)3Si>2SiMe2 respectively.Under identical conditions, from 15 an equilibrium mixture of 15 and 16 was formed, while from 19 an equilibrium mixture of 18 and 19 was formed.Isomerization of the polysilane with n = 10 produced <(Me3Si)3SiSiMe2>2 as a single product, and the polysilane with n = 12 was converted to a single isomer <(Me3Si)3SiSiMe2SiMe2>2.The 29Si NMR chemical shifts for permethylated linear polysilanes with n = 4-12 and for isomerization products are recorded.