Reaction of Borane in Tetrahydrofuran with 1,1,3,3-Tetramethyldisilazane and Cyclic Disilazanes - Competition Between N-Si and N-H Bond Cleavage

Abstract

Borane in tetrahydrofuran (THF-BH3/THF; 1) reacts with 1,1,3,3-tetramethyldisilazane (2a) and the cyclic disilazanes (2b), 3 (2c), 4 (2d)] first by formation of amine-borane adducts (3a - d), and then to give /μ-aminodiboranes(6) by H2 elimination (4a -,d) or cleavage of N-Si bonds (5a-d ), depending on the reaction conditions, in agreement with the results obtained for the reaction of 1 with hexamethyldisilazane. Further transformations proceed via the N,N-disilylaminoboranes 6a - d. In the case of the reaction between 1 and 2b, it proved possible to convert 4b and/or 5b quantitatively into the mixed diaminoborane 7b which served for the synthesis of N,N′,N″-tris[(2′-dimethylsilylethyl)dimethylsilyl]borazine (8b). The Si-H functions in 5b, 7b and 8b react with Co2(CO)8 to afford the respective Si-Co(CO)4 derivatives 11b - 13b. All compounds were characterized by their 1H , 11B, 13C, 14/15N and 29Si NMR spectra.