The crystal structures of m-trifluoromethylphenylsilatranone and p-fluorophenylsilatranone

The crystal structures of two silatranone derivatives are reported. The close N → Si approach (2.106(3) Å in m-trifluoromethylphenyl-, and 2.129(3) Å in p-fluorophenyl-silatranone) indicates strong dative acceptor bonds. For various silatrane derivatives and inverse relation has been revealed between the mean group electronegativity of the substituent R attached to silicon and the N → Si dative bond distance. In both structures there are long (1.72 Å) SiO bonds in the SiOCO moiety. The m-trifluoromethylphenyl derivative contains a disordered CF₃ group.     

Untersuchungen zur Umsetzung von [Lithium(trimethylsilyl)amido]-methyl-trimethylsilylamino-silan Me(Me3SiNLi)(Me3SiNH)SiH mit verschiedenen Elektrophilen

Investigations of the Reaction between the [Lithium(trimethylsilyl)amido]-methyl-trimethyl-silylamino-silane Me(Me₃SiNLi)(Me₃SiNH)SiH and different Electrophiles The lithium silylamide Me(Me₃SiNLi)(Me₃SiNH)SiH 1 reacts with chlorotrimethylsilan in the nonpolar solvent n-hexane to the N-substitution product Me[(Me₃Si)₂N](Me₃SiNH)SiH 2 and to the cyclodisilazane [Me(Me₃SiNH)Si—N(SiMe₃)]₂ 3 nearly in same amounts. The reaction of 1 with chlorotrimethylstannane gives besides small amounts of the cyclodisilazane 3 the N-substitution product Me[(Me₃Si)(Me₃Sn)N](Me₃SiNH)SiH 4 . By the reaction of 1 with trimethylsilyltriflate the cyclodisilazane 3 is obtained as the main product. Furthermore 2 and the cyclodisilazane 5 are formed. Ethylbromide shows no reaction with 1 under the same conditions. These results indicate the existence of an equilibrium of the lithium silylamide 1 , the silanimine Me(Me₃SiNH)Si?N(SiMe₃) and lithium hydride.     

IR-spektroskopische Untersuchungen an N-Alkyliden-alkylaminen und N-(Trimethylsilylethyliden)-alkylaminen

I.R. Spectroscopic Investigations on N-Alkylidene-alkylamines and N-(Trimethylsilylethylidene)-alkylamines The position of the C?N-stretching vibration of N-Alkylidene-alkylamines and N-(Trimethylsilylethylidene)-alkylamines in carbon tetrachloride has been determined. The relative basicity has been measured for this compounds by means of the ^vC-D band shift of CDCl₃ associated to the azomethine. The data are discussed with respect to the specific influence of the trimethylsilyl group.     

Spektroskopische Untersuchungen zu Substituenteneffekten in Silylmethylsilanen

Spectroscopic Investigations on Substituent Effects in Silylmethylsilanes The silanes Me_3?n(Me₃SiCH₂)_nSiH (n = 1–3), (RMe₂SiCH₂)₃SiH (R = n-Bu, n-Pr, Et, PhCH₂, Ph) and Me₃ElCH₂SiMe₂H (El = Ge, Sn) were prepared. The frequencies of the Si? H stretching vibration, the ²⁹Si? ¹H coupling constants and the ²⁹Si n.m.r. chemical shifts were measured. The ?(SiH) and J(²⁹Si? ¹H) values in the silanes Me_3?n(Me₃SiCH₂)_nSiH depend on the number of trimethylsilymethyl groups. There is hardly an influence of the substituents R on these values in the silanes (RMe₂SiCH₂)₃SiH. The frequencies of the Si? H stretching vibrations in the silanes Me₃ElCH₂SiMe₂H (El = Si, Ge, Sn) show the order Si?Ge > Sn. The ₂₉Si n.m.r. chemical shifts of the Si(H) signals are approximately equal in the silanes Me_3?n(Me₃SiCH₂)_nSiH and (RMe₂SiCH₂)₃SiH.     

2,8,9-Trioxa-5-aza-1-sila-bicyclo[3.3.3]undecan-3-one,ein neuer typ von silatranen; darstellung und eigenschaften

A new type of silatranes (2,8,9-trioxa-5-aza-1-silabicyclo[3.3.3] undecan-3-ones) has been prepared by reaction of organotrimethoxysilanes with N-bis(2-hydroxyethyl)aminoacetic acid.The solvolytic stability compared with that of simple acyloxysilanes, the extremely decreased basicity of nitrogen and the NMR spectra prove the pentacoordination of silicon in these compounds. Basicity and NMR data are substituent-dependent.     

Darstellung und spektroskopische Untersuchungen von hoch-verzweigten funktionellen Siloxanen

Preparation and Spectroscopic Investigations of Highly Branched Functional Siloxanes The preparation of the siloxanes [(Me₃SiO)₃SiO]_n(Me₃SiO)_3?nSiX and (Me₃SiO)₃Si[OSi(OSiMe₃)₂]₂X (n = 1?3, X = H, Cl, OC₂H₅, OH) is described. The hydride-siloxanes and the siloxanoles have been investigated by i.r. and ²⁹Si-n.m.r. spectroscopy. The frequencies of the Si? H stretching vibration, the ²⁹Si? ¹H coupling constants and the ²⁹Si-chemical shifts of the Si(H) signal for the hydride-siloxanes as well as the frequencies of the (Si)O? H stretching vibration, the relative (Si)O? H acidity, and the ²⁹Si-chemical shifts of the Si(OH) signal for the siloxanoles show a dependence on the number of the (Me₃SiO)₃SiO groups. The spectroscopic data are discussed with respect to the silicate environment of the Si(H) and Si(OH) atom, respectively. In the siloxanoles intramolecular hydrogen bondings were observed.     

Darstellung,Charakterisierung und Reaktionsverhalten von Natrium‐ und Kaliumhydridosilylamiden R2(H)Si—N(M)R′ (M = Na,K) — Kristallstruktur von [(Me3C)2(H)Si—N(K)SiMe3]2·THF

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 · THF The alkali metal hydridosilylamides R₂(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)Me₂; 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 Me₂(H)Si—NHCMe₃ ( 1a ) reacted not under metalation but under nucleophilic substitution of the H(Si) atom to give Me₂(NaNH)Si—NHCMe₃ ( 5 ). In the reaction of Me₂(H)Si—NHSiMe₃ ( 1b ) with NaNH₂ intoluene a mixture of Me₂(NaNH)Si—NHSiMe₃ and Me₂(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 ²⁹Si‐NMR‐chemical shifts and the ²⁹Si—¹H coupling constants of homologous alkali metal hydridosilylamides R₂(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 ²⁹Si‐NMR‐signals are shifted upfield and the ²⁹Si—¹H coupling constants except for compounds (Me₃C)(H)Si—N(M)SiMe₃ are decreased. The reaction behaviour of the amides 1a‐Na — 1c‐Na and 1a‐K — 1c‐K was investigated toward chlorotrimethylsilane in tetrahydrofuran (THF) and in n‐pentane. In THF the amides produced just like the analogous lithium amides the corresponding N‐silylation products Me₂(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 , 2c . In contrast to 1b‐Na and 1c‐Na and to the analogous lithium amides the reaction of 1b‐K and 1c‐K with chlorotrimethylsilane afforded the N‐silylation products Me₂(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.     

Toward the development of the direct and selective detection of nitrates by a bioinspired Mo-Cu system

The development of a new platform for the direct and selective detection of nitrates is described. Two thioether-based chemosensors and the corresponding sulfoxides and sulfones were prepared, and their photophysical properties were evaluated. Upon selective sulfoxidation of these thioethers with nitrates via an oxygen-transfer reaction promoted by a bioinspired Mo-Cu system, significant fluorescence shifts were measured. A selective response of these systems, discriminating between nitrate salts and H(2)O(2), was also shown.     

Darstellung,Eigenschaften und Reaktionsverhalten von 2-(Dimethylaminomethyl)phenyl- und 8-(Dimethylamino)naphthylsubstituierten Lithiumhydridosilylamiden – Bildung von Silaniminen durch Lithiumhydrideliminierung

Preparation, Properties, and Reaction Behaviour of 2-(Dimethylaminomethyl)phenyl- and 8-(Dimethylamino)naphthylsubstituted Lithium Hydridosilylamides – Formation of Silanimines by Elimination of Lithium Hydride The hydridosilylamines Ar(R)Si(H)–NHR′ ( 2 a : Ar = 2-Me₂NCH₂C₆H₄, R = Me, R′ = CMe₃; 2 b : Ar = 2-Me₂NCH₂C₆H₄, R = Ph, R′ = CMe₃; 2 c : Ar = 2-Me₂NCH₂C₆H₄, R = Me, R′ = SiMe₃; 2 d : Ar = 8-Me₂NC₁₀H₆, R = Me, R′ = CMe₃; 2 e : Ar = 8-Me₂NC₁₀H₆, R = Ph, R′ = CMe₃; 2 f : Ar = 8-Me₂NC₁₀H₆, R = Me, R′ = SiMe₃) have been synthesized from the appropriate chlorosilanes Ar(R)SiHCl either by reaction with the stoichiometric amount of Me₃CNHLi ( 2 a , 2 b , 2 d , 2 e ) or by coammonolysis in liquid NH₃ with chlorotrimethylsilane in molar ratio 1 : 3 ( 2 c , 2 f ). Treatment of 2 a–2 f with n-butyllithium in equimolar ratio in n-hexane resulted in the lithiumhydridosilylamides Ar(R)Si(H)–N(Li)R′ 3 a–3 f . The frequencies of the Si–H stretching vibration and ²⁹Si–¹H coupling constants in the amides are smaller than in the analogous amines indicating a higher hydride character for the hydrogen atom of the Si–H group in the amides compared to the amines. Results of NMR spectroscopic studies point to the existence of a (Me₂)N → Si coordination bond in the 8-(dimethylamino)naphthyl-substituted amines and amides. The amides 3 a–3 c are stable under refluxing in m-xylene. At the same conditions 3 d and 3 e eliminate LiH and the silanimines 8-Me₂NC₁₀H₆(R)Si=NCMe₃ ( 4 d : R = Me, 4 e : R = Ph) are formed. The amides 3 a–3 d und 3 f react with chlorotrimethylsilane in THF to give the corresponding N-substitution products Ar(R)Si(H)–N(SiMe₃)R′ 6 a–6 d and 6 f in good yields. 4 d is formed as a byproduct in the reaction of 3 d with chlorotrimethylsilane. In n-hexane and m-xylene these amides are little reactive opposite to chlorotrimethylsilane. 6 a–6 d and 6 f are obtained in very small amounts. In the case of 3 d besides the N-substitution product 6 d the silanimine 4 d is obtained. In contrast to chlorotrimethylsilane the amides 3 a and 3 f react well with chlorodimethylsilane in m-xylene producing 2-Me₂NCH₂C₆H₄(H) SiMe–N(SiHMe₂)CMe₃ ( 7 a ) and 8-Me₂NC₁₀H₆(H)SiMe–N(SiHMe₂)SiMe₃ ( 7 f ).     

Untersuchungen zur Acidität und Basizität von Alkoxysilylaminen

Investigations on Acidity and Basicity of Alkoxysilylamines Relative acidity and basicity have been determined for silylamines of the type (RO)₃Si? NH? X (R = Et, n. Pr, i-Pr, s-Bu, t-Bu; X = n-Bu, Ph, p-MeO? C₆H₄, p-Cl? C₆H₄, p-NO₂? C₆H₄) by IR, NMR, and potentiometric investigations. The position of the ν_NH band, the shift of this band in tetrahydrofuran and the chemical shift of NH-proton-NMR signal show a significant increase of NH acidity with increasing electron attracting effect of R and X. The shift of deuteriochloroform ν_CD band at association with aminosilanes and the results of potentiometric investigations confirm the low basicity of these compounds and the decrease of the basicity with increasing acidity.