Generation and capture of alkylchlorosilanones

Alkyltrichlorosilanes react with DMSO (molar ratio 1 : 1 0 °C) to give cyclic oligoalkylchlorosiloxanes of the general formula [R(Cl)SiO] _n (where R=Me or Et;n=3–6). With an excess of alkyltrichlorosilane (2: 1), linear oligoalkylchlorosiloxanes Cl[R(Cl)SiO] _m SiCl₂R (where R=Me or Et;m=1–5) are also formed. In the presence of hexamethyldisiloxane (molar ratio Cl₃SiR : DMSO: (Me₃Si)₂O=1:1:2, 20 °C), the reaction products are both cyclic and linear oligoalkyl(trimethylsilyloxy)siloxanes [R(Me₃SiO)SiO] _n (n=3–5) and Me₃Si[OSi(OSiMe₃)R] _m OSiMe₃ (m=1–3), respectively. The reaction of DMSO with trichloro(vinyl)silane and hexamethyldisiloxane occurs in a similar manner. A plausible scheme of formation of the final products via intermediate alkylchlorosilanones RClSi=O and alkyl(trimethylsilyloxy)silanones is discussed. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 361–364, February, 2000.     

Investigation of Polymerization and Cyclization of Dimethyldiethoxysilane by 29Si NMR and FTIR

Dimethyldiethoxysilane (DMDES) appears to be a very promising modifier to introduce functional groups to a silicate network. The polymerization and cyclization of DMDES under acid-catalyzed conditions (DMDES : Ethanol : water : HCl = 1:4:4:3.68 × 10^–4 in molar ratio) were investigated by high resolution liquid ²⁹Si nuclear magnetic resonance (NMR) and Fourier transform infrared spectrometry (FTIR). Time-dependent NMR and FTIR data illustrate that monomers of (CH₃)₂Si(OC₂H₅)₂, (CH₃)₂Si(OC₂H₅)(OH), and (CH₃)₂Si(OH)₂ reach meta-equilibrium in less than 4 minutes. 3-membered rings ((CH₃)₂SiO)₃ appear about half an hour later and 4-membered rings ((CH₃)₂SiO)₄ an hour later, which continue to be formed over 24 hours. The relative concentrations of monomers, linear structures and cyclic structures suggest a modified model for the kinetics of cyclization, where 4-membered rings are formed by dimer-dimer interactions, as opposed to monomer-trimer interactions previously proposed.     

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.     

Lithiierte Siloxy-silylamino-silane – Darstellung und Reaktionen mit Chlordimethylsilan

Lithiated Siloxy-silylamino-silanes — Preparation and Reactions with Chlorodimethylsilane The siloxy-silylamino-silanes (Me₃SiO)Me_3–nSi(NHSiMe₃)_n ( 1 : n = 1, 2 : n = 2, 3 : n = 3) are obtained by coammonolysis of the chlorosiloxysilanes (Me₃SiO)Me_3–nSiCl_n (n = 1–3) with chlorotrimethylsilane. The reaction of 1, 2 , and 3 with n-butyllithium in appropriate molar ratio in n-hexane gives the siloxy-silylamido-silanes (Me₃SiO)Me_3–nSi(NLiSiMe₃)_n ( 4 : n = 1, 5 : n = 2, 6 : n = 3), which were spectroscopically characterized (IR, ¹H-, ⁷Li-, ²⁹Si-NMR) and allowed to react in solution (n-hexane, THF) with Me₂Si(H)Cl. 4 reacts to the N-substitution product (Me₃SiO)Me₂SiN(SiMe₃)SiMe₂H 7, 5 to (Me₃SiO)MeSi[N(SiMe₃)SiMe₂H](NHSiMe₃) 8 , (Me₃SiO)MeSi[N(SiMe₃)SiMe₂H]₂ 9 and to the cyclodisilazane 10. 6 gives in THF the cyclodisilazanes 11 : R = H; 12 : R = HMe₂Si) and ( 13 , in n-hexane only 11 in small amounts. An amide solution of 2 with n-butyllithium in the molar ratio 1:1 in n-hexane leads to 8 (main product), 2 and 10; in THF 10 and 2 are obtained nearly in same amounts and 8 and 9 as byproducts. The amide solutions of 3 with n-butyllithium in the molar ratio 1:1 and 1:2, resp., show nearly the same behaviour in n-hexane and THF. In THF 3, 11 , and 12 and in n-hexane 3, 11, 12 , and (Me₃SiO)Si[N(SiMe₃)SiMe₂H](NHSiMe₃)₂ 14 are formed.     

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.     

Some gas phase reactions of silicenium ions derived from sym-tetramethyldisiloxane

Ion cyclotron resonance spectroscopy has been used to study reactions of the silicenium ions, Me₂HSiO iMeR (R = H and Me), generated from sym-tetramethyldisiloxane in the gas phase. These silicenium ions react with neutral sym-tetramethyldisiloxane by an addition—elimination process, to form the homologous silicenium ions, H(Me₂SiO _nSiMeR (n = 2 and 3). Analogous addition—elimination products, MeO(Me₂SiO)_nSiMeR, are derived from their reaction with methanol. Bimolecular adducts are observed in the presence of benzene and anisole, while oxygen abstraction occurs in the presence of anisole and acetone.     

Oligomeric Alkoxysilanes with Cagelike Hybrids as Cores: Designed Precursors of Nanohybrid Materials

Well‐defined alkoxysilane oligomers containing a cagelike carbosiloxane core were synthesized and used as novel building blocks for the formation of siloxane‐based hybrid networks. These oligomers were synthesized from the cagelike trimer derived from bis(triethoxysilyl)methane by silylation with mono‐, di‐, and triethoxychlorosilanes ((EtO)_nMe_3?nSiCl, n=1, 2, and 3). Hybrid xerogels were prepared by hydrolysis and polycondensation of these oligomers under acidic conditions. The structures of the products varied depending on the number of alkoxy groups (n). When n=2 and 3, microporous xerogels (BET surface areas of 820 and 510 m² g^?1, respectively) were obtained, whereas a nonporous xerogel was obtained when n=1. ²⁹Si NMR spectroscopic analysis suggested that partial rearrangement of the siloxane networks, which accompanied the cleavage of the Si–O–Si linkages, occurred during the polycondensation processes. By using an amphiphilic triblock copolymer surfactant as a structure‐directing agent, hybrid thin films with a 2D hexagonal mesostructure were obtained when n=2 and 3. These results provide important insight into the rational synthesis of molecularly designed hybrid materials by sol–gel chemistry.     

Darstellung und IR-spektroskopische Untersuchungen von Siloxysilanolen

Preparation and I.R. Spectroscopic Investigations of Siloxysilanols The preparation of siloxanols of the typs (RMe₂SiO)₃SiOH, (Me_3?nPh_nSiO)(Me₃SiO)₂SiOH, (PhMe₂SiO)_n(Me₃SiO)_3?nSiOH and Me_3?n(R′Me₂SiO)_nSiOH (n = 1?3) is described. The position of the OH-stretching vibration in carbon tetrachloride and the shift Δν of this band at assoziation with tetrahydrofuran and diethylether have been measured. The position of ν_OH band and Δν values are determined by n and by the substituents. The Δν values correlate with the σ* constants of the substituents R. Intramolecular interaction between the hydroxy group and the π electrons of phenyl substituents resp. lone pair electrons of the halogen atoms proceed in the siloxanols (XCH₂Me₂SiO)₃SiOH (X = Cl, Br, Ph) and Me_3?n(PhMe₂SiOSiMe₂O)_nSiOH (n = 1?3).     

IR- und NMR-spektroskopische Untersuchungen zu Substituenteneffekten in Siloxy- und Alkoxysilanen

I.R. and N.M.R. Spectroscopic Investigations on Substituent Effects in Siloxy and Alkoxysilanes Siloxy and alkoxysilanes of the types (RMe₂SiO)₃SiH, (RMe₂CO)₃SiH, (Me_3–nPh_nSiO)_m(Me₃SiO)_3–mSiH (m = 1—3, n = 1—3), and Me_3–n(RMe₂SiO)_nSiH (n = 1—3) have been prepared. The influence of the substituent effects through the (Me₂)Si? O- a (Me₂)C? O- group on the Si? H band is approximately equal.     

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.     

Oligodimethylsilane Initiators for Photochemical Vulcanization of Siloxane Rubber

Photolytic vulcanization of siloxane rubber films in the presence of trimethylsiloxy-substituted di- and trisilanes, oligodimethylsilanosiloxanes (Me₂SiO) _m (SiMe₂) _n , Me(Me₂SiO) _m (SiMe₂) _n Me, oligodimethylsilanes Me(Me₂Si) _n Me, and volatile pyrolysis products of polydimethylsilane was studied.     

Lithiumhydridosiloxysilylamide – Reaktionen in n-Octan und Tetrahydrofuran in Gegenwart von Chlortrimethylsilan

Lithium Hydridosiloxysilylamides – Reactions in n-Octane and Tetrahydrofuran in Presence of Chlorotrimethylsilane The hydrido-siloxy-silylamino-silanes (Me₃SiO)HSiMe(NHSiMe₃) 1 , (Me₃SiO)HSi(NHSiMe₃)₂ 2 and (Me₃SiO)₂HSi(NHSiMe₃) 3 were prepared by coammonolysis of the chlorosiloxysilanes (Me₃SiO)HSiMeCl and (Me₃SiO)_3–nHSiCl_n (n = 1, 2) with chlorotrimethylsilane. The reaction behaviour of lithiated compounds 1 , 2 and 3 has been investigated in n-octane and tetrahydrofuran (THF) in presence of chlorotrimethylsilane.     

Investigation on Optical and Biological Properties of 2-(4-Dimethylaminophenyl)benzothiazole Based Cycloplatinated Complexes

The optical and biological properties of 2-(4-dimethylaminophenyl)benzothiazole cycloplatinated complexes featuring bioactive ligands ([{Pt(Me₂N-pbt)(C₆F₅)}L] [L=Me₂N-pbtH 1 , p-dpbH (4-(diphenylphosphino)benzoic acid) 2 , o-dpbH (2-(diphenylphosphino)benzoic acid) 3 ), [Pt(Me₂N-pbt)(o-dpb)] 4 , [{Pt(Me₂N-pbt)(C₆F₅)}₂(μ-PR_nP)] [PR₄P=O(CH₂CH₂OC(O)C₆H₄PPh₂)₂ 5 , PR₁₂P=O{(CH₂CH₂O)₃C(O)C₆H₄PPh₂}₂ 6 ] are presented. Complexes 1 – 6 display ¹ILCT and metal-perturbed ³ILCT dual emissions. The ratio between both bands is excitation dependent, accomplishing warm-white emissions for 2 , 5 and 6 . The phosphorescent emission is lost in aerated solutions owing to photoinduced electron transfer to ³O₂ and the formation of ¹O₂, as confirmed in complexes 2 and 4 . They also exhibit photoinduced phosphorescence enhancement in non-degassed DMSO due to local oxidation of DMSO by sensitized ¹O₂, which causes a local degassing. Me₂N-pbtH and the complexes specifically accumulate in the Golgi apparatus, although only 2 , 3 and 6 were active against A549 and HeLa cancer cell lines, 6 being highly selective in respect to nontumoral cells. The potential photodynamic property of these complexes was demonstrated with complex 4 .     

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.     

Synthesis, structure, and magnetic properties of two novel lanthanide-organic frameworks

Two novel metal-organic frameworks, {[Eu(phen)(NDA)1.5(H2O)]}n ((1); NDA = 2,6-naphthalenedicarboxylate ions, phen = 1,10-phenanthroline) and {[Gd(phen)(NDA)1.5]·0.5H2NDA}n (2), have been synthesized under hydrothermal conditions. The structure analyses of 1 and 2 reveal that the two compounds belong to the triclinic system with space group P-1. Compound 1 features a 2D lattice structure while compound 2 displays a novel 3D architecture. The two frameworks were further characterized by elemental analyses, l...     

31P-NMR-UNTERSUCHUNGEN AN ARYLOXY-PHOSPHONIUMSALZEN

Abstract

³¹P-NMR-Messungen an CH₂Cl₂-Lösungen der Systeme R₃P/CCl₄/4-MeC₆H₄OH (R = Ph, Me₂N) liefern keinen Hinweis auf eine Beteiligung von Phosphoran-Strukturen bei der Bildung von Aryloxyphosphoniumsalzen aus diesen Komponenten oder auf das Vorliegen von Gleichgewichten zwischen Aryloxyphosphonium- und Phosphoran-Strukturen in

Lösung. Die δ ³¹P-Werte für Ph _n (Me₂N)_3-n P^⊕–Z SbClΘ₆ (Z = Cl, 4-MeC₆H₄O, 4-MeC₆H₄S; n = 0–3) werden mitgeteilt.

³¹P-NMR spectra of the systems R₃P/CCl₄/4-MeC₆H₄OH (R = Ph, Me₂N) in CH₂Cl₂ give no indication of the participation of phosphorane species in the aryloxyphosphonium salt formation or of the existence of equilibria in solution between aryloxyphosphonium and phosphoran species. δ ³¹P-chemical shifts of Ph _n (Me₂N)_3-n P^⊕–Z SbClΘ₆ (Z = Cl, 4-MeC₆H₄O, 4-MeC₆H₄S; n = 0–3) are reported.     

Reactions of trimethylsiloxychlorosilanes with lithium metal - On the mechanism of the formation of trimethylsiloxysilyllithium compounds LiSiRR’(OSiMe3)

The reaction pathway for the formation of the trimethylsiloxysilyllithium compounds (Me₃SiO)RR′SiLi (2a: R = Et, 2b: R = ⁱPr, 2c: R = 2,4,6-Me₃C₆H₂ (Mes); 2a-c: R′ = Ph; 2d: R = R′ = Mes) starting from the conversion of the corresponding trimethylsiloxychlorosilanes (Me₃SiO)RR′SiCl (1a-d) in the presence of excess lithium in a mixture of THF/diethyl ether/n-pentane at −110 °C was investigated.The trimethylsiloxychlorosilanes (Me₃SiO)RPhSiCl (1a: R = Et, 1b: R = ⁱPr, 1c: R = Mes) react with lithium to give initially the trimethylsiloxysilyllithium compounds (Me₃SiO)RPhSiLi (2a-c). These siloxysilyllithiums 2 couple partially with more trimethylsiloxychlorosilanes 1 to produce the siloxydisilanes (Me₃SiO)RPhSi-SiPhR(OSiMe₃) (Ia-c), and they undergo bimolecular self-condensation affording the trimethylsiloxydisilanyllithium compounds (Me₃SiO)RPhSi-RPhSiLi (3a-c). The siloxydisilanes I are cleaved by excess of lithium to give the trimethylsiloxysilyllithiums (Me₃SiO)RPhSiLi (2). In the case of the two trimethylsiloxydisilanyllithiums (Me₃SiO)RPhSi-RPhSiLi (3a: R = Et, 3b: R = ⁱPr) a reaction with more trimethylsiloxychlorosilanes (Me₃SiO)RPhSiCl (1a, 1b) takes place under formation of siloxytrisilanes (Me₃SiO)RPhSi-RPhSi-SiPhR(OSiMe₃) (IIa: R = Et, IIb: R = ⁱPr) which are cleaved by lithium to yield the trimethylsiloxysilyllithiums (Me₃SiO)RPhSiLi (2a, 2b) and the trimethylsiloxydisilanyllithiums (Me₃SiO)RPhSi-RPhSiLi (3a, 3b). The dimesityl-trimethylsiloxy-silyllithium (Me₃SiO)Mes₂SiLi (2d) was obtained directly by reaction of the trimethylsiloxychlorosilane (Me₃SiO)Mes₂SiCl (1d) and lithium without formation of the siloxydisilane intermediate. Both silyllithium compounds 2 and 3 were trapped with HMe₂SiCl giving the products (Me₃SiO)RR′Si-SiMe₂H and (Me₃SiO)RPhSi-RPhSi-SiMe₂H.     

“Instant Methylide” Modification of the Corey–Chaykovsky Epoxide Synthesis

Abstract

We report that Me₃S(O)⁺I^? (1) and Me₃S⁺I^? (2) form stable, dry mixtures with KOt-Bu and NaH, respectively, which remain stable upon prolonged storage (>1 year). The corresponding methylides (Me₂SO=CH₂ and Me₂S=CH₂) are generated upon addition of DMSO or DMSO/THF solutions of carbonyl compounds, cleanly affording epoxides via the Corey–Chaykovsky reaction in good yields and short reaction times (as short as 20 min when 1–2 mmol of various ketones and aldehydes were treated with a mixture of 1 and KOt-Bu at 50–60°C).     

Hydrothermal Preparation,Crystal Structure and Properties of {[ZnTCPP(EtOH)][Zn(en)]2}n(EtOH)2n with a Novel Two‐Dimensional (2‐D) Motif

A novel zinc porphyrin, {[ZnTCPP(EtOH)][Zn(en)]₂}_n(EtOH)_2n ( 1 ) (TCPP=meso‐tetra(4‐carboxyphenyl)‐porphyrin; EtOH=ethanol; en=ethylenediamine) was obtained via a hydrothermal reaction and characterized by single‐crystal X‐ray diffraction. Complex 1 crystallizes in the space group C2/c of the monoclinic system with eight formula units in a cell: a=32.465(4) Å, b=10.527(3) Å, c=31.845(3) Å, β=95.524(6) °, V=10832(4) ų, C₅₈H₅₇N₈O₁₁Zn₃, M_r=1238.23, D_c=1.518 g/cm³, S=1.005, µ(Mo Kα) =1.388 mm^?1, F(000) =5112, R=0.0650 and wR=0.1574. Complex 1 features a novel 2‐D layered motif. The spectral data of UV‐vis, FT‐IR and fluorescence are reported.     

Use of Neodymium Diiodide in the Synthesis of Organosilicon, ‐Germanium and ‐Tin Compounds

The reactivity of neodymium diiodide, NdI₂ ( 1 ), towards organosilicon, ‐germanium and ‐tin halides has been investigated. Compound 1 readily reacts with Me₃SiCl in DME to give trimethylsilane (6 %), hexamethyldisilane (4 %) and (Me₃Si)₂O (19 %). The reaction with Et₃SiBr in THF results in formation of Et₃SiSiEt₃ (17 %) and Et₃SiOBuⁿ (34 %). Alkylation of Me₃SiCl with PrⁿCl in the presence of 1 in THF affords Me₃SiPrⁿ (10 %), Me₃SiOBuⁿ (52 %) and Me₃SiSiMe₃ (1 %). The main product identified in the reaction mixture formed upon interaction of 1 with dichlorodimethylsilane Me₂SiCl₂ in THF is di‐n‐butoxydimethylsilane Me₂Si(OBuⁿ)₂ (54 %) together with minor amounts of Me₂Si(OBuⁿ)Cl. The reaction of 1 with Me₃GeBr under the same conditions produces Me₃GeGeMe₃ (44 %), Me₃GeH (3 %), and Me₃GeI (7 %). An analogous set of products was obtained in the reaction with Et₃GeBr. Treatment of trimethyltin chloride with 1 causes reduction of the former to tin metal (74 %). Me₃SnH (7 %) and hexamethyldistannane (11 %) were identified in the volatile products. The reaction of 1 with Me₃SiI provides straightforward access to hepta‐coordinated NdI₃(THF)₄ ( 2 ), the structure of which was determined by X‐ray diffraction.