Beiträge zur Chemie der Silicium-Schwefel-Verbindungen. XXIX. 29Si-NMR-Untersuchungen

Contributions to the Chemistry of Silicon-Sulphur Compounds. XXIX. ²⁹Si-N.M.R. Investigations Three series of silicon-sulphur compounds (RO)₃SiSR′ (I), (i-PrO)_4?nSi(SEt)_n (II) and cyclic Si? S compounds (III) were prepared, some of them at the first time and their ²⁹Si-N.M.R. spectra were measured. In the series of trialkoxysilylthio derivatives (I) were the steric and inductive effects of the RO and R'S groups evaluated. In the series II were the ²⁹Si-N.M.R. chemical shifts related to the relative paramagnetic screening constants σ^* and netto charge at the silicon atom q(Si) using the EN-quantum-chemical model discussed. In the series III were the shift contribution of the (SiS)₂ and 1-sila-2,5-dithiacyclopentan rings determined.     

Beiträge zur Chemie der Silicium-Schwefel-Verbindungen. 44. Trialkoxysilylthioderivate der Permethylpolysilane

Contributions to the Chemistry of Silicon-Sulphur Compounds. 44. Trialkoxysilylthio Derivatives of Permethylpolysilanes By reaction of (RO)₃SiSH · NEt₃ (R = i-Pr, t-Bu) with α,ω-Cl₂(SiMe₂)_n (n = 1, 2, 3, 4, 6) or with 1-Cl(SiMe₂)_nMe (n = 2, 4) trialkoxysilylthio derivatives of polysilanes of the two series α,ω-(RO)₃SiS(SiMe₂)_nSSi(OR)₃ and 1-(RO)₃SiS(SiMe₂)_nMe have been prepared. Some properties of obtained new compounds were given. The resistance of the Si? S bond on protolytic splitting has been characterized by half-life times of the alcoholysis reaction.     

29Si and 13C NMR spectra of permethylpolysilanes

²⁹Si, ¹³C and ¹H NMR spectra are reported for the series of linear permethylpolysilanes Me(SiMe₂)_nMe where n = 1 to 6, for the cyclic permethylpolysilanes (Me₂Si)_n where n = 5 to 8, and for a few related compounds. For linear polysilanes the ²⁹Si and ¹³C chemical shifts can be accurately calculated from simple additivity relationships based on the number of silicon atoms in α, β, γ and δ positions. Adjacent (α) silicon atoms lead to upfield shifts in the ²⁹Si and ¹³C resonances, whereas more remote silicon atoms lead to downfield shifts. The ²⁹Si chemical shifts of the polysilane chains are linearly related to the ¹³C shifts of the carbon atoms attached to the silicon. The ²⁹Si and ¹³C resonances of the cyclic silanes deviate from this relationship. Ring current effects arising from σ delocalization are suggested as an explanation for the deviations. Proton-coupled ²⁹Si NMR spectra are reported for Me₃SiSiMe₃ and for (Me₂Si)_n, n = 5 to 7.     

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.     

29Si-Chemische Verschiebungen in Alkoxy(amino)silanen

²⁹Si Chemical Shifts of Alkoxy(amino)silanes The ²⁹Si NMR spectra of a series of alkoxy(amino)silanes (RO)_nMe_3?nSiNHC₆H₄X (n = 1–3) have been measured and are discussed by means of relative paramagnetic screening constants σ*, calculated by a simplified quantum-chemical model. The Hammett plots of the silicon chemical shift show both positive and negative slopes with changes of the number of electronegative atoms (O, N) attached to silicon. The steric and electronic shift contributions of the alkoxy groups are given.     

Structure of novel N-fluorosilylmethyl-N-isopropylureas

Novel N-isopropyl-N',N'-dimethyl-N-(silylmethyl)ureas Me₂NC(O)N(Prⁱ)CH₂SiMe_nX_3–n (X = OEt, F; n = 0–2) were synthesized, and their structure was confirmed by ¹H, ¹³C and ²⁹Si NMR spectroscopy. According to NMR data, the silicon atom of the fluorosilanes (X = F) is pentacoordinated. The X-ray diffraction analysis of the (trifluorosilyl)methylcontaining urea showed that it exists as (O–Si) chelate with intramolecular dative bond C=O→Si (1.880 Å).     

Elektronische und sterische Effekte in 29Si-NMR-Spektren von Amino-substituierten Silanen

Electronic and Steric Effects in ²⁹Si N.M.R. Spectra of Amino-substituted Silanes Compounds of three series of amino-substituted silanes, Me_nSi(NR′R″)_4—n′, Me_3-n (RO)_nSiNR′R″, and (RO)_nSi(NR′R″)_4—n, (n = 0 ÷ 3), were prepared and characterized. ²⁹Si N.M.R. spectra have been measured. The electronic and steric shift contributions of the NR′R″ groups are given and discussed on the basis of a quantum-chemical model. The mass spectra also have been recorded and the fragmentation schemes for silanes multi substituted with amino groups are presented.     

Neutrale Bora-Silatropie an B-Halogen-substituierten Boryl-bis(silyl)hydroxylaminen

Neutral Rearrangement between Boryl and Silyl Groups in B-Halogenosubstituted Boryl-bis(silyl)hydroxylamines Dihalogenboranes, RBX₂, react with lithiated N,O-Bis(trimethylsilyl)hydroxylamine to give B-halogeno-borylhydroxylamines RB(X)ON(SiMe₃)₂: X = F, R = Trip (Trip = 2,4,6-triisopropylphenyl) ( I a ), N(SiMe₃)₂ ( I b ), N(CHMe₂)₂ ( I c ), N(SiMe₃)Dip (Dip = 2,6-diisopropylphenyl) ( I d ) and X = Cl, R = N(SiMe₃)₂ ( I e ). Depending upon the substituents on the boron atom a dyotropic rearrangement can be effected which transforms the compounds I a , I b und I e into the isomeric borylhydroxylamines RB(X)N(SiMe₃)OSiMe₃ II a , II b and II e . The compounds are characterized by their m. s. and n. m. r. (¹H, ¹¹B, ¹³C, ¹⁹F, ²⁹Si) spectra and by elemental analyses.     

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.     

Silicon-29 NMR studies of polymethylhydrosiloxanes: Spin-lattice relaxation time (T1) measurements

²⁹Si NMR spectra of polymethylhydrosiloxanes, Me₃SiO[MeHSiO]_nSiMe₃ from n = 3 to 8 and 35, have been determined. Both chemical shifts and spin-lattice relaxation times (T₁) have been measured. The stereochemistry at the adjacent chiral MeHSiO unit influences the nearest neighbor ²⁹Si chemical shift. The effect of chain length and position of MeHSiO units on T₁ values for Me₃SiO[MeHSiO]_nSiMe₃ systems are discussed.     

Reaktionen von Lithiumhydridosilylamiden RR′(H)Si–N(Li)R″ mit Chlortrimethylsilan in Tetrahydrofuran und unpolaren Lösungsmitteln: N‐Silylierung und/oder Cyclodisilazanbildung

Reactions of Lithium Hydridosilylamides RR′(H)Si–N(Li)R″ with Chlorotrimethylsilane in Tetrahydrofuran and Nonpolar Solvents: N‐Silylation and/or Formation of Cyclodisilazanes The lithiumhydridosilylamides RR′(H)Si–N(Li)R″ ( 2 a : R = R′ = CHMe₂, R″ = SiMe₃; 2 b : R = R′ = Ph, R″ = SiMe₃; 2 c : R = R′ = CMe₃, R″ = SiMe₃; 2 d : R = R′ = R″ = CMe₃; 2 e : R = Me, R′ = Si(SiMe₃)₃, R″ = CMe₃; 2 f – 2 h : R = R′ = Me, f : R″ = 2,4,6‐Me₃C₆H₂, g : R″ = SiH(CHMe₂)₂, h : R″ = SiH(CMe₃)₂; 2 i : R = R′ = CMe₃, R″ = SiH(CMe₃)₂) were prepared by reaction of the corresponding hydridosilylamines RR′(H)Si–NHR″ 2 a – 2 i with n‐butyllithium in equimolar ratio in n‐hexane. The unknown amines 1 e – 1 i and amides 2 f – 2 i have been characterized spectroscopically. The wave numbers of the Si–H stretching vibrations and ²⁹Si–¹H coupling constants of the amides are less than of the analogous amines. This indicates a higher hydride character for the hydrogen atom of the Si–H group in the amide in comparison to the amines. The ²⁹Si‐NMR chemical shifts lie in the amides at higher field than in the amines. The amides 2 a – 2 c and 2 e – 2 g react with chlorotrimethylsilane in THF to give the corresponding N‐silylation products RR′(H)Si–N(SiMe₃)R″ ( 3 a – 3 c , 3 e – 3 g ) in good yields. In the reaction of 2 i with chlorotrimethylsilane in molar ratio 1 : 2,33 in THF hydrogen‐chlorine exchange takes place and after hydrolytic work up of the reaction mixture [(Me₃C)₂(Cl)Si]₂NH ( 5 a ) is obtained. The reaction of the amides 2 a – 2 c , 2 f and 2 g with chlorotrimethylsilane in m(p)‐xylene and/or n‐hexane affords mixtures of N‐substitution products RR′(H)Si–N(SiMe₃)R″ ( 3 a – 3 c , 3 f , 3 g ) and cyclodisilazanes [RR′Si–NR″]₂ ( 6 a – 6 c , 6 f , 6 g ) as the main products. In case of the reaction of 2 h the cyclodisilazane 6 h was obtained only. 2 c – 2 e show a very low reactivity toward chlorotrimetyhlsilane in m‐xylene and toluene resp.. In contrast to Me₃SiCl the reactivity of 2 d toward Me₃SiOSO₂CF₃ and Me₂(H)SiCl is significant higher. 2 d react with Me₃SiOSO₂CF₃ and Me₂(H)SiCl in n‐hexane under N‐silylation to give RR′(H)Si–N(SiMe₃)R″ ( 3 d ) and RR′(H)Si–N(SiHMe₂)R″ ( 3 d ′) resp. The crystal structures of [Me₂Si–NSiMe₃]₂ ( I ) ( 6 f , 6 g and 6 h ) have been determined.     

29Si NMR Spektroskopie von Cyclopentasilanen

The structure and ²⁹Si chemical shifts of the halodimethylsilylnonamethylcyclopentasilanes Si₅Me₉SiMe₂X (1–4) and the halononamethylcyclopentasilanes Si₅Me₉X (5–8) (X = F, Cl, Br, I) have been assigned using ¹J(SiSi) and ²J(SiSi) coupling constants derived from ²⁹Si-INADEQUATE and ²⁹Si-INEPT—INADEQUATE NMR spectra. The compounds exhibit good correlation between chemical shift, ¹J(SiSi) and Pauling electronegativities.     

Beiträge zur Chemie der Silicium-Schwefel-Verbindungen. XLIII. Alkoholyse von Silicium-Schwefel-Verbindungen mit Alkoxyethanolen und 2-Mercaptoethanol

Contributions to the Chemistry of Silicon-Sulphur Compounds. XLIII. Alcoholysis Reaction of Silicon-Sulphur Compounds with Alkoxyethanols and 2-Mercaptoethanol The reactions of 2-alkoxyethanols und 2-mercaptoethanol with (RO)₃SiSH, (RO)₂Si(SH)₂, cyclo-[(t-BuO₂)SiS]₂, and SiS₂ were investigated. Besides of mixed esters of orthosilicic acid a new group of mixed trialkoxysilanethiols – (RO)₂(R′O)SiSH – was obtained. Informations about the hydrolytic splitting of the Si? S bond of these Si? S compounds were obtained by thiomercurimetric titration with HMB.     

Basizität und 29Si-NMR-spektroskopische Untersuchungen von Ethoxysiloxanen

Basicity and ²⁹Si N.M.R. Spectroscopic Investigations of Ethoxysiloxanes Ethoxysiloxanes of the types (RMe₂SiO)₃SiOEt, Me_3?n(R₃SiO)_nSiOEt, [(Me₃SiO)₃SiO]_n(Me₃SiO)_3?nSiOEt (n = 1–3), and (Me₃SiO)₃Si[OSi(OSiMe₃)₂]₂OEt have been prepared. The relative basicity of the (Si)OEt group and the ²⁹Si n.m.r. chemical shifts of the Si(OEt) signal were determined. The relative basicity as well as the ²⁹Si n.m.r. chemical shifts depend on the kind and number of the siloxy groups. Basicity and ²⁹Si n.m.r. chemical shifts of the respective types of compounds are connected directly with each other.     

29Si and 13C NMR spectra of chloro- and fluoro-substituted linear permethylpolysilanes

²⁹Si and ¹³C NMR spectra are reported for the three halopolysilane series Me(SiMe₂)_nCl, Cl(SiMe₂)_nCl and F(SiMe₂)_nF, where n = 2 to 6. Except for the dihalodisilanes (XSiMe₂)₂, data for all of the compounds fit linear relationships based on substituent constants for chlorine or fluorine atoms in the α, β and γ positions. The effects of halogen substitution on ²⁹Si and ¹³C chemical shifts are rapidly attenuated along the polysilane chain, becoming negligible four atoms away from the halogen. The NMR data provide no evidence for long-range electronic transmission from chlorine or fluorine in halopermethylpolysilanes of the type suggested by other workers [1].     

13C and 29Si chemical shifts and coupling constants involving tris[(trimethylsilyl)methyl] silicon compounds

Silicon-29(δ²⁹Si) NMR chemical shifts are reported for the first time of tris[(trimethylsilyl)methyl] silicon compounds (disilylated derivatives) (Me₃Si^A)₃ C_αL, where L = Si^BR₁R₂R₃ and where R varies widely in electronegativity. ²⁹Si chemical shifts exhibit good correlation with the electronegativities of the groups bonded to the silicon atom. The ¹³C NMR spectra of these compounds have been recorded and assigned. δ¹³C_α is shown to depend on the type of substitutent on Si^B. The variation of ²⁹SiH coupling constants with electronegativity of R is studied.     

Fourier transform NMR studies of organometallic compounds. II—synthesis and NMR spectroscopy of propenyl and isopropenyl derivatives of silicon and lead

Isomeric mixtures of compounds Me_nM(CH?CHMe)_4?n (M=Si, Pb; n=0?3) have been prepared and studied, as well as pure Me₃M(CMe?CH₂) and mixtures containing propenyl isopropenyl residues bonded to silicon and lead. ¹H, ¹³C, ²⁹Si and ²⁰⁷Pb NMR data are presented; as previously observed for the corresponding tin compounds, the ²⁹Si and ²⁰⁷Pb shifts for the Me₃MC₃H₅ isomers can be used to calculate the shifts expected for the other isomers; while for lead the agreement is good, calculated and observed values for silicon diverge with decreasing n due, at least in part, to steric factors.     

Neue Alkalimetall‐Koordinationen durch chelatisierende Siloxazaneinheiten in Verbindungen der Formel [X–N–SiMe2–O–SiMe2–N–X]2M4

New Alkali Metal Coordinations by Chelating Siloxazane Units within Molecules of the General Formula [X–N–SiMe₂–O–SiMe₂–N–X]₂M₄ New solvent free alkali metal amides with Si–O–Si bridges of the general formula [X–N–SiMe₂–O–SiMe₂–N–X]₂M₄ (X = ^tBu ( 1 ), SiMe₃ ( 2 ), SiMe₂^tBu ( 3 ) with M = Li; X = ^tBu ( 4 ), SiMe₃ ( 5 ) with M = Na; X = ^tBu mit M = K, Li ( 6 )) have been synthesised and characterised by spectroscopic means. X‐ray structure analyses of the six metal derivatives reveal a common structural principle: the four metal atoms within the molecules are incorporated between two molecular halfs and form the bonding links between the two parts. The central molecular skeleton of the molecular halfs consists of a zig‐zag chain N–Si–O–Si–N. This chain is connected to the second one either ideally or approximately by S₄ (4) symmetry. The point symmetries within the crystal are either S₄ (4) (compounds 2 and 4 ), C₂ (2) (compound 6 ), and C₁ (1) (compounds 3 and 5 ). Compound 1 is special in different aspects: the molecule has the high crystallographic point symmetry D_2d (4m2) and the lithium atoms occupy split atom positions (in a similar way as in compound 2 ). The high symmetry of 1 as well as the split atom positions of the lithium atoms are a consequence of dynamics within the crystal.     

The synthesis and reactivity of polysilylacetylenes: Diels—Alder reactions to give bis (silyl) benzenes

Six bis(silyl)acetylenes (XMe²Si? C?C? SiMe₂X) with the following varied silicon substituents X were prepared: 1 (Me, Me); 2 (H, H); 3 (C1, H); 4 (CI, CI); 5 (MeO, H); 6 (MeO, MeO). While 1 and 2 may be prepared by the reaction of dilithio- or bis(bromomagnesium)-acetylide with the appropriate chlorosilane, similar reactions designed to give 3–6 yielded oligomers, XMe₂Si? (? C?C? SiMe₂)_n? X, 7, X=CI, MeO, as the major products, indicating that the acetylenic functionality on silicon activates the chlorosilane towards nucleophilic substitution. Compounds 3 and 4 were prepared by free radical chlorination of 2. Methanolysis of 3 and 4 gave quantitative yields of 5 and 6 respectively. Compounds 1–6 undergo a Diels–Alder reaction with α-pyrone to produce, after loss of carbon dioxide, bis(silyl)-substituted benzene derivatives. The order of reactivity has been determined to be: 4=6>3=5>1>2, indicating that chloro or alkoxy substituents favor the cycloaddition with 2- pyrone. The adducts formed by compounds 3–6 undergo an unusually facile hydrolysis or elimination to give 1,1,3,3-tetramethyl-1,3-disila-2-oxaindane.     

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.