Darstellung und einige Eigenschaften von Silylderivaten der hyposalpetrigen Säure und ihrer Amide

Preparation and Some Properties of Silyl Derivatives of Hyponitrous Acid and of its Amides Bis(trimethylsilyl)hyponitrite Me₃SiO? N?N? OSiMe₃ ( 1 ) is formed by reaction of Ag₂N₂O₂ with Me₃SiCl and of (Me₃Si)₂NOLi with SO₂Cl₂. Tris(trimethylsilyl)-1-hydroxytriazen ( 2 ) is formed by reaction of (Me₃Si)₃N₂Li and i-amyl nitrite. The thermolysis of 1 leads to nitrogen, trimethylsilanol, and hexamethyldisiloxane, the thermolysis of 2 leads to hexamethyldisiloxane and trimethylsilylazide. HO? N?N? NH₂ could not be isolated as a product of protolysis of 2. 2 is converted into LiO? N?N? N(SiMe₃)₂ ( 4 ) by LiNR₂ (R = Me, SiMe₃), 4 is converted into MeO? N?N? N(SiMe₃)₂ ( 5 ) by Me₂SO₄. The thermolysis of 4 leads to LiN₃ and (Me₃Si)₂O, the thermolysis of 5 leads to Me₃SiN₃ and Me₃SiOMe.     

Ionische Strukturen von 4- bzw. 5fach koordiniertem Silicium Neue ionische Festkörperstrukturen von 4- bzw. 5fach koordiniertem Silicium: [Me3Si(NMI)]+Cl−, [Me2HSi(NMI)2]+Cl−, [Me2Si(NMI)3]2+ 2 Cl−· NMI

Ionic Structures of 4- and 5-coordinated Silicon. Novel Ionic Crystal Structures of 4- and 5-coordinated Silicon: [Me₃Si(NMI)]⁺ Cl^?, [Me₂HSi(NMI)₂]⁺ Cl^?, [Me₂Si(NMI)₃]²⁺ 2 Cl^?. NMI Me₃SiCl forms with N-Methylimidazole (NMI) a crystalline 1:1-compound which is stable at room temperature. The X-ray single crystal investigation proves the ionic structure [Me₃Si(NMI)]⁺Cl^? 1 which is the result of the cleavage of the Si? Cl bond and the addition of an NMI-ring. The reaction of Me₂HSiCl with NMI (in the molar ratio of 1:2), under cleavage of the Si? Cl bond and co-ordination of two NMI rings, yields the compound [Me₂HSi(NMI)₂]⁺Cl^? 2 . The analogous reaction of Me₂SiCl₂ with NMI (molar ratio 2:1) leads to a compound which consists of Me₂SiCl₂ and NMI in the molar ratio of 1:2. During the sublimation single crystals of the compound [Me₂Si(NMI)₃]²⁺ 2 Cl^?. NMI 3 are formed.     

Reaktionen von TaCl5, MoCl5 und WCl6 mit Bis(trimethylsilyl) carbodiimid

Reactions of TaCl₅, MoCl₅, and WCl₆ with Bis(trimethylsilyl)carbodiimide When TaCl₅ reacts with Me₃SiNCNSiMe₃ (Me = CH₃) in a 1:1 molar ratio, 1 mol Me₃SiCl and dimeric [Cl₄TaNCNSiMe₃]₂ is formed. The vibrational spectra (IR and Raman) show a planar structure of approximate C_2h symmetry. Polymeric [Cl₄WNCN]_n is formed by the reaction of WCl₆ and Me₃SiNCNSiMe₃, but 2 mol Me₃SiCl result in this 1:1 molar interaction. On the other hand MoCl₅ and Bis(trimethylsilyl)carbodiimide (molar ratio 2:1) forms polymeric [(Cl₄Mo)₂NCN]_n, a compound with Mo? N? Mo and Mo—(Cl₂)—Mo bridges. The IR spectra of these carbodiimide derivatives are used for structural suggestions.     

Silylamides of group IVA and IVB elements with spirobicycloheptane structure

Spirocyclic metal silylamides with spiro[3.3]heptane structure, M′  Si, Ge, Sn, Ti, Zr and Hf, have been prepared. Except for the Si derivative, the synthesis involved

the reaction of the appropriate M′Cl₄ with Me₃SiN(M)SiMe₂-N(M)SiMe₃, M  Li, Na. The M′  Si derivative was obtained via reaction of IIIb with NH₃, subsequent treatment with butyllithium and Me₃SiCl, and then ring closure with Me₂SiCl₂. The new compounds have been characterized by analyses, NMR, IR, Raman and mass spectra. The metallaspiranes are thermally stable to > 200°C, are very volatile, and do not form complex with ether.     

The reaction of trimethylchlorosilane with phenyltelluromagnesium bromide in tetrahydrofuran: Characterisation of the products by 29Si and 125Te NMR spectroscopy

The products of the reaction of Me₃SiCl with PhTeMgBr in THF have been identified with the aid of high resolution ²⁹Si and ¹²⁹Te NMR spectroscopy. In addition to the expected product Me₂SiTePh (40%), the symmetrical telluride (Me₃Si)₂Te (10%) and the ether Me₃SiO(CH₂)₄TePh (45%) are also formed. The latter results from ring-opening of the solvent THF by Me₃SiCl followed by reaction of the product with PhTeMgBr.     

Synthese,Eigenschaften und Struktur von oktamerem Titanimidchlorid [Ti(NSiMe3)Cl2]8

Synthesis, Properties, and Structure of Octameric Titanium Imide Chloride [Ti(NSiMe₃)Cl₂]₈ The reaction of TiCl₄ with N(SiMe₃)₃ in sealed glas-tubes yields the titanium imide chloride [Ti(NSiMe₃)Cl₂]₈ ( 1 ). It crystallizes in the space group C2/c with a = 2 704.5(4), b = 1 303.9(1), c = 2 205.4(2) pm, β = 112.78(1)°, Z = 4. In 1 six Ti atoms are linked together by chloro and trimethylsilylimido bridges to form a ring structure. Two TiCl₂-groups are bound in addition to the ring by two imido bridges. Upon annealing at 250°C 1 transformes to the isomeric polymer [Ti(NSiMe₃)Cl₂]_n. Above 250°C 1 decomposes under separation of Me₃SiCl affording TiNCl.     

Contributions to the chemistry of halosilane adducts: XVIII. On the nature of compounds of trimethylhalosilanes with 1,1,3,3-tetramethylguanidine and 2-trimethylsilyl-1,1,3,3-tetramethylguanidine: preparation and characterization of mono- and bis-(2-trimethylsilyl)-1,1,3,3-tetramethylguanidinium halides

1,1,3,3-Tetramethylguanidine (TMG) and 2-(trimethylsilyl)-1,1,3,3-tetramethylguanidine (TMSTMG) react with trimethylhalosilanes Me₃SiHal in equimolar ratio with ionization of the Sihalogen bond to give the stable guanidinium salts [(Me₂N)₂CNHSiMe₃]Hal (Hal  Cl (1), Br (2)) and [(Me₂N)₂CN(SiMe₃)₂]Hal (Hal  Cl (3), Br (4), I (5)), respectively, involving tetracoordinate silicon. No reaction occurs with Me₃SiF. The same ionic species are present in CHCl₃ or CH₃CN solutions (IR, ¹H, ²⁹Si NMR), thus establishing for the first time, the formation of an ionic solid derivative of Me₃SiCl stable towards dissociation. Reaction with an excess of TMG gives an equilibrium mixture of TMSTMG and TMG · HHal. The bis(silyl)guanidinium salts are less stable towards dissociation than the mono(silyl) derivatives, the stability sequence being Cl⁻ < Br⁻ < I⁻ within the series. The reactions of both types of compound have been investigated. The implications of the present and earlier results for the mechanisms of racemization and nucleophilic substitution at silicon are discussed.     

Nouvelles syntheses de Me2SiCl2 et Me3SiCl

Partial reduction of MeSiCl₃ and Me₂SiCl₂ using CaH₂ or (TiH₂)_n at high temperature (300°C) leads to MeSiHCl₂ and Me₂SiHCl, respectively, in good yields but in low proportion. In the presence of AlCl₃ as catalyst the reaction affords Me₂SiCl₂ and Me₃SiCl, in yields higher than those previously observed in the absence of a reducing agent. These redistribution reactions involve MeSiHCl₂ and Me₂SiHCl as intermediates. Consequently Me₂SiHCl with or without Me₂SiCl₂ and Alcl₃ deposited on carbon black as catalyst can undergo disproportionation to give Me₃SiCl.     

N,N-Bis(trimethylsilyl)dithiocarbazinsäure-S-methylester: Darstellung,Struktur und Reaktionen mit Halogenverbindungen des Titans,Niobs, Tantals und Molybdäns

N,N-bis(trimethylsilyl)-S-methyldithiocarbazate. Preparation, Molecular Structure, and Reactions with Titanium, Niobium, Tantalum, and Molybdenum Halides The reaction of Me₃SiCl with NH₂NHC(S)SMe yields as single product the title compound (Me₃Si)₂Nnhc(S)SMe ( 1 ). The Si₂NNC(S)S moiety is not planar. The Si? N-distances are in the range 176.9(8) to 178.1(9) pm. 1 does not react to hydrazido or diazenido complexes with Cp₂TiCl₂, CpTiCl₃, MCl₅ and CpMCl₄ (M = Nb, Ta). With MoO₂Cl₂(dmso)₂ the dimeric compound (dmso)₂Mo(μ-NNC(S)SMe)₂Mo(O)Cl₂ is obtained.     

Monocarboxylates of 3-Methylidene-β-lactams: Synthesis and unusual oxidative rearrangement into a spiro[azetidine-3,3′-pyrrolidine] derivative

Reaction of the 3-silylated β-lactams 1 with glycoxalates gives bis-lactam 3 , but the same reaction in the presence of 1 equiv. of Me₃SiCl leads to the formation of the disilylated adducts 5 . The latter is desilylated by (Bu₄N)F yielding the monocarboxylates 7 of 3-methylidene-β-lactams, which, with oxidizing agents, give the spiro compound 8 . The structure of 8 is established by spectroscopic data and a crystal-structure analysis.     

Silver Salts of the Weakly Coordinating Anion [Me3NB12Cl11]–

Silver(I) salts of weakly coordinating anions (WCA) are commonly applied as oxidizing agents or halide abstracting reagents. The feasibility of a particular silver salt for such applications strongly depends on the “nakedness“ of the silver cation. In this study the reactivity of Ag[Me₃NB₁₂Cl₁₁] in different solvents was investigated. Crystal structures of a variety of complexes were obtained. In several crystal structures two boron clusters are bridged by Ag–Cl contacts. This leads to polymeric structures (e.g. for Ag[Me₃NB₁₂Cl₁₁]·0.5CH₂Cl₂ and Ag[Me₃NB₁₂Cl₁₁]·SO₂). Sterically demanding aromatics like mesitylene, pyrene, and acenaphthene are η¹‐ or η²‐bonded to the silver atom and also form coordination polymers, whereas benzene as a ligand leads to a molecular structure, in which two benzene molecules are η²‐coordinated to the silver cation. In contrast, strong σ donor ligands like pyridine and triphenylphosphine give homoleptic silver complexes and thus cation and anion are separated. Furthermore, the ability of Ag[Me₃NB₁₂Cl₁₁] for performing metathesis reactions was investigated. The reaction with Au^ICl gave the [Au(NCMe)₂]⁺ cation.     

Convenient,high yield syntheses of [Nb(O)Cl3], [Nb(O)Cl3(CH3CN)2] and [NB(O)Cl3(THF)2]. Formation and decomposition of intermediate alkoxo (and siloxo) derivatives of general formula [NbCl4(OR)]2 (R = Me,Et, SiMe3)

Trimethylsilylaklylethers, Me₃SiOR (R = Me, Et) and hexamethyldisiloxane react with NbCl₅ in dichloromethane under ambient conditions to give readily isolable mono-alkoxides, [NbCl₄(OR)]₂ (R = Me, 1; Et, 2) and the thermally sensitive siloxide [NbCl₄(OSiMe ₃)]₂ (3), respectively. At 80°C in 1,2-dichloroethane, 1–3 undergo efficient conversion to [Nb(O)Cl₃] with elimination of RCl. In acetonitrile solution, the reaction of NbCl₅ with (Me₃Si)₂O proceeds smoothly to give [Nb(O)Cl₃(CH₃CN)₂] which is readily converted to [Nb(O)Cl₃(THF)₂] upon dissolution in tetrahydrofuran (THF).     

Utility of trichloroisocyanuric acid in the efficient chlorination of silicon hydrides

The potential of trichloroisocyanuric acid (TCCA) as a chlorination agent for efficient conversion of Si-H functional silanes and siloxanes to the corresponding Si-Cl functional moieties was explored. In comparison to methods using other chlorinating agents, TCCA is inexpensive, results in a much faster reaction and produces a high purity product with a conversion that is essentially quantitative. A variety of chloro derivatives of linear and cyclic structures have been synthesized from silicon hydrides using this reagent with impressive yields that typically exceed 90%: PhSiCl₃ (97.5%); PhMeSiCl₂ (95.5%); Ph₃SiCl (97.5%); Vi₃SiCl (98.7%); (EtO)₃SiCl (99.7%); t-Bu₃SiCl (∼100%); (MeClSiO)₄ (86.5%); (MeClSiO)₅ (95%); (MeClSiO)₇ (96.5%); Ph(OEt)₂SiCl (98%); ClMe₂SiOSiMe₂Cl (98.6%); ClMe₂SiOSiMeClOSiMe₂Cl (94.6%); ClMe₂Si(OSiMeCl)₂OSiMe₂C l (92.3%); (Me₃SiO)₃SiCl (97%); Me₃SiOSiClPhOSiMe₃ (99%); Me₃SiO(SiMeClO)₃SiMe₃ (95.7%); ClSi(OSiMe₃)₂OSi(OSiMe₃) ₂Cl (93.6%).For monohydridosilanes, dichloromethane (CH₂Cl₂) was a suitable solvent in which nearly quantitative conversion was observed within several minutes following the addition of the silanes to TCCA. For certain cyclic and linear siloxanes, and especially silanes containing multiple hydrogen atoms on the same silicon for which the reaction is sluggish in CH₂Cl₂, tetrahydrofuran (THF) was the preferred solvent. For a sterically demanding silane that did not undergo chlorination even in THF viz., HSi(OSiMe₃)₂O-Si(OSiMe₃)₂H, 1,2-dichloroethane was the best solvent.     

8-Oxyquinolate iridium(I) complexes and their oxidative-addition reactions

The novel sixteen-electron complex [Ir(Oq)(COD)] (Oq = 8-oxyquinolate; COD = 1,5-cyclooctadiene) adds monodentate phosphines, phosphites or activated olefins irreversibly to give pentacoordinate iridium(I) complexes of the type [Ir(Oq)(COD)L] (L = PPh₃, P(OPh)₃, maleic anhydride or tetracyano-ethylene). Reaction of [Ir(Oq)(COD)] with some diphosphines leads to substitution products of the general formula [Ir(Oq)(diphos)] (diphos = 1,2-bis(diphenylphosphino)ethane or cis-1,2-bis(diphenylphosphino)ethylene). Carbon monoxide displaces the COD group from the complexes giving either [Ir(Oq)(CO)₂] or [Ir(Oq)(CO)L], and the latter undergo oxidative addition reactions with SnCl₄, Me₃SiCl, Me₃SnCl, MeI, allylbromide, PhCOCl, MeCOCl, Cl₂, Br₂, TlCl₃ and HCl leading to novel iridium(III) complexes.     

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.     

Synthesen von Heterocyclen, 133. Mitt.: Zur Chlorierung von 4-Hydroxy-2-pyridonen

Zusammenfassung Die Chlorierung des 5-Äthoxycarbonyl-4-hydroxy-6-methyl-2-pyridons (1) mit SO₂Cl₂ gibt bei unterschiedlichen Reaktionsbedingungen die chlorierten Derivate2,3 bzw.4. Bei der Reaktion des 4-Hydroxy-6-phenyl-2-pyridons (5) mit SO₂Cl₂ erhält man das 3,3,5-Trichlor-pyridin-2,4-dion (6), das mittels Zn/Eisessig zum Dichlorderivat7 reduziert wird. Durch Hydrolyse von6 und Decarboxylierung entsteht das Enaminketon8.

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Syntheses of heterocycles, CXXXIII: Concerning the chlorination of 4-hydroxy-2-pyridones

Chlorination of ethyl 4-hydroxy-6-methyl-2-pyridone-5-carboxylate (1) with SO₂Cl₂ gives, depending on the reaction conditions, the chlorinated derivatives2,3 and4. The reaction of 4-hydroxy-6-phenyl-2-pyridone5 with SO₂Cl₂ yields 3,3,5-trichloro-pyridin-2,4-dione (6), which can be reduced with Zn/AcOH to give 3,5-dichloro-4-hydroxy-2-pyridone (7). Hydrolysis of6 and decarboxylation leads to the enaminoketone8.

     

Structural studies in main group chemistry : XIX. Organotin(IV) derivatives of tetracyanoethylene, 7,7,8,8-tetracyanoquinodimethane and 2,3,5,6-tetrachlorobenzoquinone. The isolation of stable organotin-substituted radicals

The reaction of organotin chlorides with the lithium salt of 7,7,8,8-tetracyanoquinodimethane (TCNQ) or hexaalkylditins with TCNQ yield stable organotin-substituted free radicals of the types R₃SnTCNQ^. (R = Me, n-Pr, n-Bu) and Me₂Sn(TCNQ^.)₂. The reaction of hexaphenylditin with TCNQ yields a (σ → π) charge transfer complex of stoichiometry (Ph₃SnSnPh₃)·TCNQ, whilst [Me₂SnCl(terpyridyl)⁺](TCNQ^-·) was isolated from the reaction of [Me₂SnCl(terpyridlyl)⁺][Me₂SnCl₃^-] and LiTCNQ. The oxidation of hexaalkylditins by tetracyanoethylene (TCNE) yields stable free radicals of the type R₃SnTCNE·, but treatment with 2,3,5,6-tetrachlorobenzoquinone yields either R₃SnOC₆Cl₄O·-p (R = Me) or R₃SnOC₆Cl₄OSnR₃-p (R = n-Bu, Ph). Tin-119 Mössbauer spectroscopy shows that the derivatives R₃SnTCNQ· and R₃TCNE· have trigonally-bipyramidally coordinated tin with planar [SnC₃] skeletons and bridging [TCNQ·] and [TCNE·] groups forming infinite one-dimensional chain structures. Me₃SnOC₆Cl₄O·-p was inferred to possess a similar structure but with oxy bridges forming chains with a Sn---O---Sn---O backbone. Me₂Sn(TCNQ·)₂ has a structure intermediate between tetrahedral and octahedral with a non-linear MeSnMe unit and anisobidentate chelation by two TCNQ groups. The TCNQ derivatives were of two types: (i) “green” or “brown”, indicative of delocalisation of the Ione electron over the cyanoquinone ligand, and (ii) a “blue” form in which spin-pairing of the Ione electron between adjacent organic groups takes place. Me₃SnTCNQ· may exist in both forms depending upon the mode of preparation.     

Cross-Coupling Versus Homo-Coupling Reactions with Benzyl Bromide,Magnesium and Chlorotrimethylsilane

The selective synthesis of benzyltrimethylsilane from PhCH₂Br, Mg and Me₃SiCl requires a low reaction temperature.     

Living cationic polymerization of vinyl ethers by electrophile/lewis acid initiating systems. VII. Living cationic polymerization of isobutyl vinyl ether by trimethylsilyl halide/zinc halide initiating systems in the presence of p-methoxybenzaldehyde: Effects of halide anions and zinc halides

Trimethylsilyl halides (Me₃SiY), in conjunction with zinc halides (ZnX₂) (Y and X:I, Br, Cl), were employed to investigate the living cationic polymerization of isobutyl vinyl ether (IBVE) in toluene at ?15°C in the presence of p-methoxybenzaldehyde; with the aldehyde and IBVE monomer, Me₃SiY yields an initiating species [Me₃Si? O? CHC₆H₄(OM_e) ? CH₂CH(OiBu) ? Y] that triggers the IBVE polymerization via the activation of its carbon-halogen bond (C? Y) by ZnX₂ into C^δ+…?Y^δ?…?ZnX₂. Living polymerizations occurred with the silyl iodide and bromide irrespective of the type of ZnX₂, either when Y = X (Me₃Sil/Znl₂ and Me₃SiBr/ZnBr₂) or when Y ≠ X (Me₃Sil/ZnBr₂, Me₃SiI/ZnCl₂, and Me₃SiBr/Znl₂). With these five initiating systems, the number-average molecular weights (M?_n) of the polymers increased in proportion to monomer conversion, and the molecular weight distributions (MWDs) of the polymers were narrow (M?_w/M?_n = 1.1?1.2). The Me₃SiCl-based systems (Me₃SiCl/ZnCl₂ and Me₃SiCl/Znl₂), in (Me₃SiCl/Znl₂), in contrast, failed to give perfectly living polymerization; the M?_n indeed increased with conversion, but the MWDs of the polymers were broader (M?_w/M?_n = 1.3?1.5). Thus, the living nature of the polymerizations with Me₃SiY/Znx₂ is primarily determined by the halogen Y in Me₃SiY, which generates the terminal carbon-halogen bond (C? Y) that is activated by ZnX₂ for the propagation via a species C^δ+…?Y^δ?…?ZnX₂. For Y^?, not only the iodide but the bromide anion also is suited for living cationic polymerization. The virtual absence of the effects of X in ZnX₂ implies that the halogen exchange between ZnX₂ and Y from Me₃ SiY at the growing end (C^λ+…?Y^δ?…?ZnX₂ ?C^δ+…?X^δ?…?ZnXY) is absent or negligible.     

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.