Asymmetric tris- and cyclic silylhydroxylamines from trimeric and tetrameric lithium N,N-bis(silyl)hydroxylamides

The fluorosilylhydroxylamine (BuSiF)-Bu-t(Me)-ONH2 (2) is obtained in the r eaction of tBuSiF(Me)-(NHBu)-Bu-t (1) and HONH2. KCl. The reaction by (BuSi Me2)-Bu-t-ONH2 with butyllithium leads to the formation of the bis(silyl)hy droxylamine (BuSiMe2)-Bu-t-NH-O-SiF(Me)Bu-t (3). Depending on the bulkiness of the substituents and the solvent, lithium salts of N,O-bis(silyl)hydrox ylamines crystallize as dimeric, trimeric, or tetrameric O-lithium-N,N-bis( silyl)hydroxylamides, e.g., [((BuSiMe2)-Bu-t)(2)N-OLi.THF](2), [((BuSiMe2)- Bu-t)(2)N-OLi](3) (4), and [(BuSiMe3)-Bu-t(Me3Si)N-OLi](4) (6). Lithiation of (BuSiMe2ONHSiMe2Bu)-Bu-t-Bu-t in the presence of TMEDA leads to a cleava ge of the N-O bond. The hexameric lithium silanolate ((BuSiMe2O)-Bu-t-Li)(6 ) (5) is obtained. Above 0 degreesC the Lithium derivative of 3 (3a) reacts with LiF and the cyclic silylhydroxylamine ((BuSiMe)-Bu-t-O-N-(SiMe2Bu)-Bu -t)(2) (7). In the reactions of 3a and 6 with F2SiMe2 and F3SiMe the first asymmetrical tris(silyl)hydroxylamines N,N-(BuSiMe2)-Bu-t(FSi(Me)Bu-t)N-O-S iFMe2 (8), N,N-(BuSiMe2)-Bu-t(SiMe3)N-O-SiFMe2 (9), N,N-(BuSiMe2)-Bu-t(SiMe 3)N-O-SiF2Me (10), and the bis((bie)(silyl)hydroxylamino)silane [N,N-(BuSiM e2)-Bu-t(SiMe3)](2)-O-SiFMe (11) are isolated. Chlorodimethylalane reacts w ith the trimericO-lithium-N,N-bis(tert-butyldinl amide to give LiCl and the four-membered ring system 2,4-bis-N,N-bis(tert-butyldimethyl-silylhydroxgi lamide)-1-dimethylalano-3-lithio (12). Crystal structures of 4-7 and 12 are reported.