REACTIONS OF H(PHMESI)3H WITH TRIFLIC ACID - EVIDENCE FOR REARRANGEMENT PROCESSES

The reaction of the trisilane, H(PhMeSi)(3)H, with 1 or 2 equiv of triflic acid (HOTf) followed by quenching with MeMgBr resulted in the formation of two isomers each of Ph(2)Me(4)Si(3)H(2) and PhMe(5)Si(3)H(2), respectively. When H(PhMeSi)(3)H was treated with 3 equiv of triflic acid and quenched with PhMgBr, two isomers of Ph(3)Me(3)Si(3)H(2) were formed. The isomers formed in the sequence with 1 equiv of HOTf result from competitive cleavage of internal SiPh bonds vs terminal SiPh bonds, as demonstrated by labeling experiments. The products formed from reaction with a second and third equivalent of trific acid require a rearrangement process and may be rationalized through a common cationic intermediate, [HMe(TfO)SiSiMesi(X)MeH](+) OTf(-) (X = Ph, OTf).