Thermal Isomerisation of Tris(silyl)hydroxylamines to Silylaminodisiloxanes − Experimental and Quantum Chemical Results

Abstract

O-Lithio-N,N-bis(trimethylsilyl)hydroxylamide, LiO−N(SiMe3)2, reacts with ClSiMe2H to give HMe2Si−O−N(SiMe3)2 (1), while LiO−N(SiMe2CMe3)2 reacts with C6H5SiF3 to give C6H5SiF2−O−N(SiMe2CMe3)2 (2). 2 isomerises in solution to give N,O-bis(tert-butyldimethylsilyl)-N-[difluoro(phenyl)silyl]hydroxylamine (3). Boiling of 1 leads to the structurally isomeric silylaminodisiloxane, Me3Si−O−SiMe2−NH−SiMe3 (4), while boiling of 3 leads to the isomeric Me3CSiMe2−O−Si(Me)CMe3−NMe−SiF2C6H5 (5). Quantum chemical calculations (B3LYP) on the thermal rearrangement of tris(silyl)hydroxylamines to silylaminodisiloxanes for the model compounds H3Si−O−N(SiMe3)2 (A), Me3Si−O−N(SiH3)2 (B), Me3Si−O−N(SiH3)SiMe2F (C), and Me3Si−O−N(SiMe2F)SiMeF2 (D) demonstrate that N-bonded silyl units, e.g. SiH2 in model compound B or SiFMe in model compound D, preferentially insert into the N−O bond. The reaction mechanisms and the structures of the transition states are discussed in detail. (© Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)