Reaction of tris(trimethylsilyl)methylsilicon halides with methanolic sodium methoxide. Probability of sila-olefin intermediates

The compounds TsiSiR₂X [Tsi = Me₃Si)₃C; R = Me, X = Cl, Br, I, or R = Ph, X = F, Cl, Br, I)] react with boiling 2 M MeONa-MeOH to give products of the type (Me₃Si)₂CHSiR₂OMe. It is suggested that the reaction proceeds through an elimination, analogous to E2 eliminations of alkyl halides, involving synchronous attack of MeO^? at an Me₃Si group, liberation of X^?, and formation of (Me₃Si)₂CSiR₂. The compounds TsiSiPhMeF TsiSiPhCl₂ react analogously to give (Me₃Si)₂CHSiPhMe(OMe) and (Me₃Si)₂CHSiPh(OMe)₂ [tha latter presumably by solvolysis of the initially-formed (Me₃Si)₂CHSiPhCl(OMe)]. The compounds TsiSiMe₂OMe and TsiSiMe₃ do not react, while TsiSiMe₂H gives TsiH. The compound TsiSiCl₃ reacts with 0.1 M MeONa-MeOH to give the substitution and elmination products TsiSiCl₂(OMe) and (Me₃Si)₂CHSi(OMe)₃ in ca. $\text{1}\text{2}$ ratio.     

The Cyclohexasilanes Si6H11X and Si6Me11X with X=F,Cl, Br and I: A Quantum Chemical and Raman Spectroscopic Investigation of a Multiple Conformer Problem

The conformers of the monohalocyclohexasilanes, Si₆H₁₁X (X=F, Cl, Br or I) and the haloundecamethylcyclohexasilanes, Si₆Me₁₁X (X=F, Cl, Br or I) are investigated by DFT calculations employing the B3LYP density functional and 6‐31+G* basis sets for elements up to the third row, and SDD basis sets for heavier elements. Five minima are found for Si₆H₁₁X—the axial and equatorial chair conformers, with the substituent X either in an axial or equatorial position—and another three twisted structures. The equatorial chair conformer is the global minimum for the X=Cl, Br and I, the axial chair for X=F. The barrier for the ring inversion is ～13 kJ mol^?1 for all four compounds. Five minima closely related to those of Si₆H₁₁X are found for Si₆Me₁₁X. Again, the equatorial chair is the global minimum for X=Cl, Br and I, and the axial chair for X=F. Additionally, two symmetrical boat conformers are found as local minima on the potential energy surfaces for X=F, Cl and Br, but not for X=I. The barrier for the ring inversion is ～14–16 kJ mol^?1 for all compounds. The conformational equilibria for Si₆Me₁₁X in toluene solution are investigated using temperature dependent Raman spectroscopy. The wavenumber range of the stretching vibrations of the heavy atoms X and Si from 270–370 cm^?1 is analyzed. Using the van′t Hoff relationship, the enthalpy differences between axial and equatorial chair conformers (H_ax?H_eq.) are 1.1 kJ mol^?1 for X=F, and 1.8 to 2.8 kJ mol^?1 for X=Cl, Br and I. Due to rapid interconversion, only a single Raman band originating from the “averaged” twist and boat conformers could be observed. Generally, reasonable agreement between the calculated relative energies and the experimentally determined values is found.     

Die chemie der schweren carben-analogen R2M,M = Si,Ge, Sn: X. 7-sila-norbornadiene: reaktionen mit halogenen und thermolyse in genewart von metallorganischen oder organischen halogeniden

The 7-sila norbornadienes (I–IV) react rapidly with halogens at −20 to +20°C to yield Me₂SiHal₂ (Hal = Cl, Br, I) and the naphthalene or benzene derivatives (V–VIII). Bromine in CCl₄ at 0°C, however, caused surprising rearrangement in I giving the 2-bromosilylated naphthalene (IX), since an attack at the alkene group seemed to be preferred. Methylation and methoxylation of IX gave respectively X and XI. Careful hydrolysis of IX yielded the disiloxane VII. Insertions of Me₂Si into the SiHal, SiH, SiC, or SnC bonds were not observed at 160–200°C, whereas insertions into SnCl or SnH bonds occurred smoothly via a one-step mechanism. Halogen is abstracted from different CHal bonds leading to Me₂SiHal₂ and sometimes to Me₄Si₂Hal₂. The degradation of the silylene precursors in these cases is always first order and resembles that of spontaneous thermolysis.     

1,3-Migration of chloride and azide substituents within organosilicon cations,and anchimeric assistance by the azido group

Migration of the Cl substituent takes place when (Me₃Si)₂C(SiMe₂Cl)(SiEt₂I) or (Me₃Si)₂C(SiEt₂Cl)(SiMe₂I) reacts with AgBF₄, the product in each being a mixture of (Me₃Si)₂C(SiEt₂Cl)(SiMe₂F) and (Me₃Si)₂C(SiEt₂F)(SiMe₂Cl), and analogous migration of N₃ occurs in the corresponding reaction of (Me₃Si)₂C-(SiEt₂N₃)(SiMe₂Br). Anchimeric assistance by the N₃ group facilitates the solvolysis of (Me₃Si)₂C(SiMe₂N₃)(SiMe₂Br).     

Cyclische Diazastannylene. XXXII. Zur Synthese und Reaktivität difunktionalisierter Cyclosilagermadiazane—Bildung von Digermanen

Cyclic Diazastannylenes. XXXII. On the Synthesis and Reactivity of Difunctional Cyclosilagermadiazanes—Formation of Digermanes The cyclic bisaminostannylene Me₂Si(t-BuN)₂Sn 1 reacts with tetrahalides of germanium GeX₄(X = Cl, Br, I) forming the bisaminodihalogengermanes 2a, 2b and 2c. The halogen atoms of the compounds 2 may be substituted by alkyl-, amino- and pseudohalide groups: Me₂Si(t-BuN)₂GeXY (X = Y = N₃ 3 ; X = Br, Y = Me 4 , Y = t-Bu 6 , Y = N(SiMe₃)₂ 8a , Y = NEt₂ 9 ; X = Me, Y = N₃ 5a , Y = CN 5b ; X = N₃, Y = t-Bu 7 , Y = N(SiMe₃)₂ 10 ; X = I, Y = N(SiMe₃)₂ 8b ). Reduction of the compounds 2b and 4 with sodium naphthalide generates the digermanes (Me₂Si(t-BuN)₂GeR)₂ (with R = Br 11 , R = Me 12 ) Compound 8b crystallizes in the monoclinic space group P2₁/c with Z = 8 and lattice constants a = 16.205(8), b = 19.854(9), c = 17.537(9) Å, β = 107.50(9)°. Compound 11 crystallizes in the triclinic space group P1 with Z = 2 and lattice constants a = 8.921(4), b = 11.091(5), c = 17.590(8) Å, α = 80.5(1), β = 89.2(1), γ = 71.4(1)°.     

Reaktionen von Bortrihalogeniden mit Tris-(trimethylsily)-amin

Interaction of Borontrihalides and Tris-(trimethylsilyl)-amine According to the reaction conditions and the used halides borontrihalides BX₃ (X = F, Cl, Br) and tris-(trimethylsily1)-amine, (Me₃Si)₃N, I, (Me ? CH₃—) interact to give MeBX₂, (Me₃Si)₂N? BMeX, (Me₃Si)₂N? BX₂ or mixtures of these compounds; e. g. BF₃, and I yield (Me₃Si)₂N? BF₂ and Me₃SiF, while BBr₃ and I at 23°C form MeBBr₂ and (Me₃Si)₂NSiMe₂Br. In addition the unknown aminoboranes (Me₃Si)₂N? BMe₂ and (Me₃Si)₂N? BMeBr were synthesized using a different route.     

1,3-Migration of a phenyl group in the conversion of (Me3Si)2(PhMe2Si)CSiMePhX into (Me3Si)2(Ph2MeSi)CSiMe2Y species

The finding that compounds of the type (Me₃Si)₂(PhMe₂Si)CSiMePhX react with electrophiles to give very predominantly rearranged products (Me₃Si)₂(Ph₂MeSi)CSiMe₂Y, which would be expected to be thermodynamically disfavoured, can be rationalized in terms of a mechanism in which the anchimerically-assisted departure of X⁻ gives the Ph-bridged cation [(Me₃Si)₂

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MePh]⁺ which is attacked by the nucleophile at the less hindered centre bearing two Me groups rather than that bearing one Me and one Ph group, with the outcome determined by kinetic rather than thermodynamic factors. Both (Me₃Si)₂(Ph₂MeSi)CSiMe₂Br and its isomer (Me₃Si)₂(PhMe₂Si)CSiMePhBr react with AgBF₄ in CH₂Cl₂ or Et₂O to give >95% of the fluoride (Me₃Si)₂(Ph₂MeSi)CSiMe₂F. Reaction of the bromide (Me₃Si)₂(PhMe₂Si)CSiMePhBr with AgO₂CCF₃ in Et₂O, and that of the hydride (Me₃Si)₂(PhMe₂Si)CSiMePhH with ICl in CCl₄, likewise give >95% of the rearranged (Me₃Si)₂(Ph₂MeSi)CSiMe₂O₂CCF₃ and (Me₃Si)₂(Ph₂MeSi)CSiMe₂Cl, respectively.     

NMR-spektroskopische Untersuchungen an Undecamethylcyclohexasilanyl-Derivaten

The structure and ²⁹Si chemical shifts of nine undecamethylcyclohexasilanyl derivatives, Si₆Me₁₁X (X = Fe(CO)₂cp, SO₃CF₃, F, Cl, Br, I, H, C CH, OH), have been assigned using ¹J_SiSi and ²J_SiSi derived from ²⁹Si-INADEQUATE and ²⁹Si-INEPT-INADEQUATE and ²⁹Si-INEPT-INADEQUATE NMR spectra. Only the halo-derivatives exhibit linear correlation between ¹J_SiSi and Pauling electronegativities. The correlation of other derivatives is improved by employing Inamato's inductivity values. A new synthetic route to Si₆Me₁₁X (X = F, Cl, Br, I) has been developed.     

Chemistry and Structures of Hexakis(halogenomethyl)‐, Hexakis(azidomethyl)‐, and Hexakis(nitratomethyl)disiloxanes

An investigation of the structures and chemistry of substituted hexamethyl disiloxanes ((XCH₂)₃Si)₂O; X=F, Cl, Br, I, N₃, and ONO₂) is reported. New synthetic routes to the precursor hexakis(chloromethyl)disiloxane are presented. The products with X=Cl, Br, I, and N₃ were characterized by NMR, IR, and Raman spectroscopy. In addition, the single‐crystal structures of the products with X=Cl, Br, and I are discussed in detail. The compounds with X=F and ONO₂ were not obtained in their pure form; instead investigations of the decomposition products revealed their conversion into intermediates. Theoretical calculations of the gas‐phase structures at the B3LYP/cc‐pVDZ, B3LYP/3‐21G, MP2/6‐31G*, and MP2/3‐21G levels of theory are used to explain the chemical and physical behavior of the compounds with X=Cl, Br, I, N₃, and ONO₂. A new decomposition pathway of hexakis(nitratomethyl)disiloxane is presented and is used to explain their remarkable instability. The energetic properties and values of the nitrate and azide derivatives were calculated at the CBS‐4M level of theory by using the improved EXPLO5 computer code version 6.01.     

Untersuchungen an Selen-Verbindungen. LXIX. Über das Reaktionsverhalten von Diphenylselendihalogeniden mit Ammoniak,Alkyl- und Silylaminen

Studies on Selenium Compounds. LXIX. On the Reactivity of Diphenyl Selenium Dihalides with Ammonia, Alkyl- and Silylamines The halides Ph₂SeX₂ (Ph = C₆H₅; X = Cl, Br) are reduced by NH₃, MeNH₂ and Me₂NH (Me = CH₃) at ?60°C forming Ph₂Se. The reaction of Ph₂SeCl₂ with Me₃SiNMe₂ yields Ph₂Se(NMe₂)Cl, whereas with (Me₃Si)₂NH the salt [Ph₂Se?N?SePh₂]Cl is formed. The infrared spectra are presented and discussed.     

Formation of Methane versus Benzene in the Reactions of (C5Me5)2Th(CH3)2 with [CH3PPh3]X (X=Cl,Br, I) Yielding Thorium‐Carbene or Thorium‐Ylide Complexes

The reaction of (C₅Me₅)₂Th(CH₃)₂ with the phosphonium salts [CH₃PPh₃]X (X=Cl, Br, I) was investigated. When X=Br and I, two equivalents of methane are liberated to afford (C₅Me₅)₂Th[CHPPh₃]X, rare terminal phosphorano‐stabilized carbenes with thorium. These complexes feature the shortest thorium–carbon bonds (≈2.30 Å) reported to date, and electronic structure calculations show some degree of multiple bonding. However, when X=Cl, only one equivalent of methane is lost with concomitant formation of benzene from an unstable phosphorus(V) intermediate, yielding (C₅Me₅)₂Th[κ²‐(C,C′)‐(CH₂)(CH₂)PPh₂]Cl. Density functional theory (DFT) investigations of the reaction energy profiles for [CH₃PPh₃]X, X=Cl and I showed that in the case of iodide, thermodynamics prevents the production of benzene and favors formation of the carbene.     

Synthesis of Silver Complexes in DMSO–HX and DMSO–HX–Ketone Systems

Comparative analysis of the oxidizing and complexing properties of the DMSO–HX (X = Cl, Br, I) and DMSO–HX–ketone (X = Br, I; the ketone is acetone, acetylacetone, or acetophenone) systems toward silver was performed. The reaction products are AgX (X = Cl, Br, I), [Me₃S⁺]Ag _n X^– _m (n= 1, 2; m= 2, 3; X = Br, I) and [Me₂S⁺CH₂COR]AgX^– ₂(R = Me, Ph; X = Br, I). The composition of the obtained complexes depends on both the DMSO : HX ratio and the nature of HX, as well as on the methods used to isolate solid products from the solution. It was noted that the formation of the [Me₂S⁺CH₂COMe]AgBr^– ₂complex in the Ag⁰–DMSO–HBr–acetylacetone system occurs with cleavage of the acetylacetone C–C bond and follows a specific reaction course. The optimum conditions for production of the silver compounds in the title systems are determined.     

Formation of Methane versus Benzene in the Reactions of (C5Me5)2Th(CH3)2 with [CH3PPh3]X (X=Cl,Br, I) Yielding Thorium‐Carbene or Thorium‐Ylide Complexes

The reaction of (C₅Me₅)₂Th(CH₃)₂ with the phosphonium salts [CH₃PPh₃]X (X=Cl, Br, I) was investigated. When X=Br and I, two equivalents of methane are liberated to afford (C₅Me₅)₂Th[CHPPh₃]X, rare terminal phosphorano‐stabilized carbenes with thorium. These complexes feature the shortest thorium–carbon bonds (≈2.30 Å) reported to date, and electronic structure calculations show some degree of multiple bonding. However, when X=Cl, only one equivalent of methane is lost with concomitant formation of benzene from an unstable phosphorus(V) intermediate, yielding (C₅Me₅)₂Th[κ²‐(C,C′)‐(CH₂)(CH₂)PPh₂]Cl. Density functional theory (DFT) investigations of the reaction energy profiles for [CH₃PPh₃]X, X=Cl and I showed that in the case of iodide, thermodynamics prevents the production of benzene and favors formation of the carbene.     

Reactions of xenon difluoride: Oxidative fluorination of methyl derivatives of the p-block elements

A survey has been carried out to determine how xenon difluoride reacts with methyl derivatives of p-block elements, Me_nX (n = 3, X = N, P, As, or Sb; n = 2, X = O, S, or Se; n = 1, X = Cl, Br, or I), on the basis of NMR measurements, tensimetric and IR analysis of the gaseous products, and mass balances. The reaction proceeds smoothly in most cases, although a Freon like CCl₃F may be needed as a moderator; the rate of the reaction seems to reflect the basicity of the substrate Me_nX. The difluoride Me_nXF₂ is formed in the cases where X = P, As, Sb, Se, or I. The scope of xenon difluoride in these conditions as a mild selective oxidative fluorinating agent is illustrated by the synthesis of the known compounds (CF₃)₂XF₂ (X = S or Se) and the novel compound Me(CF₃)SeF₂. By contrast, cleavage of CH bonds, with the formation of CH₂F derivatives, is the predominant path in the cases where X = N, O, or S, and cleavage of CX bonds, with the formation of MeF, occurs in the cases where X = Cl or Br.     

Tris(trimethylsilyl)methanselenenylhalogenide und -chalkogenide

Tris(trimethylsilyl)methaneselenenyl Halides and Chalcogenides . Ditrisyldiselenide ( 1 ) (trisyl = TSi = (Me₃Si)₃C) reacts with SOCl₂, Br₂ and I₂ to provide trisylselenenyl halides TSiSeX ( 2 : X = Cl; 3 : X = Br, 4 : X = I). Insertion of S and Se into the Se? Se bond of 1 to yield (TSiSe)₂S_n ( 5 : n = 1; 6 : n = 2) and (TSiSe)₂Se_n ( 7 : n = 1; 8 : n = 2) was catalysed by iodine. 5 was isolated in pure state and examined by X-ray diffraction. Triselenide 7 can be cleaved by I₂ in CS₂ to give 4 and Se₂I₂ ( 9 ). From 2 with Me₃SiCN and Me₃SiNCS, the new selenenyl pseudohalides TSiSeCN ( 10 ) and TSiSeSCN ( 11 ) were prepared. The compounds were characterised by ¹H, ¹³C- and ⁷⁷Se n.m.r. spectra.     

Reactions of polyfluoroaromatic compounds with electrophilic agents in the presence of tris(dialkylamino)phosphine

The rate of replacement of the halogen atom in isomers of RC₆F₄X (X=Cl, Br, or I) by the SiMe₃ group under the action of Me₃SiCl and P(NEt₂)₃ depends on the nature and the mutural arrangement of the substituents X and R. In addition to silyldehalogenation, compounds C₆HF₄X (X=Br or I) undergo silyldeprotonation and reduction to tetrafluorobenzenes. For Part 5, see Ref. 1 Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 813–818, April, 1997.     

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.     

Neue Synthesen von Me2SbX (X = Cl,I) und Kristallstrukturen von Me2SbI und [(Me3Si)2CH]2SbCl

Novel Syntheses of Me₂SbX (X = Cl, I) and Crystal Structures of Me₂SbI and [(Me₃Si)₂CH]₂SbCl The crystal structures of Me₂SbI (Me = CH₃) and [(Me₃Si)₂CH]₂SbCl have been determined by X‐ray methods. Both molecules are pyramidal. The Me₂SbI molecules are associated to chains through short intermolecular Sb…I distances (366,7(1) pm) with linear I–Sb…I units (171,87(4)°) and bent Sb–I…Sb bridges (116,83(3)°).     

N,N,N′,N′-Tetramethylethylendiamin-di(tert-butyl)aluminium-Kationen — Molekülstruktur des [(Me3C)2Al · TMEDA]⊕[(Me3C)2AlBr2]⊖

(N,N,N′,N′ -tetramethylethylendiamine) di(tert-butyl)aluminium Cations — Molecular Structure of [(Me₃C)₂Al(TMEDA)]^⊕[(Me₃C)₂AlBr₂]^? Dimeric di(tert-butyl)aluminium halides (Me₃C)₂AlX (X = Cl, Br) react with N,N,N′,N′ -tetramethylethylendiamine (TMEDA) to give three compounds: the salt-like [(Me₃C)₂Al(TMEDA)]^⊕[(Me₃C)₂AlX₂]^? 1 , characterized by crystal structure determination, and [(Me₃C)₂Al(TMEDA)]^⊕X^? 3 both with chelating amine, and the more covalent, pentane soluble (Me₃C)₂AlX(TMEDA) 2 with TMEDA bound by only one nitrogen atom. The reaction resembles the symmetrical and unsymmetrical cleavage of diborane(6). 3 (X = Cl) is also formed by treatment of 1 with boiling n-hexane in the presence of TMEDA over a period of 24 hours, while for X = Br the more covalent 2 is the main product under similar conditions. In solution 2 decomposes slowly yielding different products in dependency of the solvent: in benzene 3 and in n-pentane 1 are formed.     

Über siliciumschwefel-verbindungen : III. Neue organylthiosilane

Novel organylthio(alkoxy)silanes (I, II, III and XII) and organylthio(diethylamino)silanes (IV, V) are described. They were prepared by treating lithium or lead thiolates with the corresponding chlorosilanes or by cleavage of dimethylbis(diethylamino)silane with thiols. Phenylthiosilanes (Me₃SiSPh, III and XIII) furthermore can be obtained by reaction of chlorosilanes with benzenethiol in the presence of tertiary amines. The SiS bond of Me₃SiSPh is cleaved by chlorosilanes like Me₂Si(NEt₂)Cl or Me₂Si(OPr)Cl. This reaction is a convenient route to prepare compounds I and IV. The physical and chemical properties of the novel compounds were investigated.