Preparation, characterization and reaction behaviour of sodium and potassium hydridosilylamides R2(H)Si-N(M)R' (M=Na, K) -: Crystal structure of [(Me3C)2(H)Si-N (K)SiMe3]2•2THF

The alkali metal hydridosilylamides R-2(H)Si-N(M)R' 1a-Na-1d-Na and 1a-K-1d-K (a: R = Me, R' = CMe3; b: R = Me, R' = SiMe3; c: R = Me, R' = Si(H)Me-2; d: R = CMe3, R' = SiMe3) have been prepared by reaction of the corresponding hydridosilylamines 1a-1d with alkali metal M (M = Na, K) in presence of styrene or with alkali metal hydrides MH (M = Na, K). With NaNH2 in toluene Me-2(H)Si-NHCMe3 (1a) reacted not under metalation but under nucleophilic substitution of the H(Si) atom to give Me-2(NaNH)Si-NHCMe3 (5). In the reaction of Me-2(H)Si-NHSiMe3 (1b) with NaNH2 intoluene a mixture of Me-2(NaNH)Si-NHSiMe3 and Me-2(H)Si-N(Na)SiMe3 (1b-Na) was obtained. The hydridosilylamides have been characterized spectroscopically. The spectroscopic data of these amides and of the corresponding lithium derivatives are discussed. The Si-29-NMR-chemical shifts and the Si-29-H-1 coupling constants of homologous alkali metal hydridosilylamides R-2(H)Si-N(M)R' (M = Li, Na, K) are depending on the alkali metal. With increasing of the ionic character of the M-N bond M = K > Na > Li the Si-29-NMRsignals are shifted upfield and the Si-29-H-1 coupling constants except for compounds (Me3C)(H)Si-N(M)SiMe3 are decreased. The reaction behaviour of the amides 1a-Na-1e-Na and 1a-K-1c-K was investigated toward chlorotrimethylsilane in tetrahydrofuran (THF) and in n-pentane. In THF the arnides produced just like the analogous lithium amides the corresponding N-silylation products Me-2(H)Si-N(SiMe3)R' (2a-2c) in high yields. The reaction of the sodium amides with chlorotrimethylsilane in nonpolar solvent n-pentane produced from 1a-Na the cyclodisilazane [Me2Si-NCMe3]2 (8a), from 1b-Na and 1-Na mixtures of cyclodisilazane [Me2Si-NR'](2) (8b, 8c) and N-silylation product 2b, 2e. In contrast to 1b-Na and 1c-Na and to the analogous lithium amides the reaction of 1b-K and 1e-K with chlorotrimethylsilane afforded the N-silylation products Me-2(H)Si-N(SiMe3)R' (2b, 2c) in high yields. The amide [(Me3C)(2)(H)Si-N(K)SiMe3](2).THF (9) crystallizes in the space group C2/c with Z = 4. The central part of the molecule is a planar four-membered K2N2 ring. One potassium atom is coordinated by two nitrogen atoms and the other one by two nitrogen atoms and one oxygen atom. Furthermore K...H(Si) and K...CH3 contacts exist in 9. The K-N distances in the K2N2 ring differ marginally.