PUB - Publikationen an der Universität Bielefeld

The use of tri(alkoxy)silanes (RO)(3)SiH, which have recently become commercially available in greater than research scale quantities (R = Me, Et), has been probed for the preparation of hydrogen-rich arylsilanes ArSiH3. It was found that the silylation of aryl-lithium or (in situ) aryl-Grignard reagents is followed by RO/H ligand redistribution and can lead to fully hydrogenated products in a one-pot reaction without employment of any additional metal hydride. After hydrolytic workup, the overall yields are between 20 and 30%. Silane gas and tetra(alkoxy)silanes are the main byproducts. At an early stage of the reactions, the whole set of mixed-ligand silanes (RO)(3-n)HnSiAr can be detected by GLC/MS techniques. Induced by the organometallic base, the reaction also includes aryl scrambling to give silanes ArnSiH4-n, ArnSi(OR)(4-n), and ArnSi(H/OR)(4-n). A reaction scheme is proposed that accounts for the product distribution. Examples are given for Ar = phenyl, 4-biphenylyl, 4,4'-biphenyldiyl, 1-naphthyl, and 2-anisyl. The reaction gives only very poor yields of di(silyl)arenes. Silanes of this type were therefore prepared from (RO)3SiH compounds and the corresponding di(halo)arenes by the in situ Grignard procedure followed by LiAIH(4) reduction. Representative cases-are 1,2- and 1,4-di(silyl)benzene and 1,4-di(silyl)-2,5-dimethylbenzene. The primary reaction products 1,4-(EtO)(3)SiC6H4Si(OEt)(3) and 1,4[(EtO)(3)Si](2)-2,5-(CH3)(2)C6H2 have been isolated, and the crystal structure of the latter was determined.