Synthesen und Charakteristika von Heterobimetallorganika des Siliciums mit dem 2‐(Dimethylaminomethyl)ferrocenyl‐Liganden FcN (η5‐C5H5)Fe[η5‐C5H3(CH2NMe2)]—

Syntheses and characteristics of the heterobimetalorganics of the silicon with the 2‐(dimethylaminomethyl)ferrocenyl ligand FcN (η⁵‐C₅H₅)Fe[η⁵‐C₅H₃(CH₂NMe₂)]^— The heterobimetallic lithiumorganyl [2‐(dimethylaminomethyl)ferrocenyl] lithium, LiFcN, reacts with silicon(IV)‐chlorid, SiCl₄, under the formation of heterobimetallic silicon(IV) organyl [(FcN)₃SiCl] ( 1 ). The heterobimetallic organosilanol [(FcN)₃SiOH] ( 2 ) is formed at hydrolysis of 1 . A detailed characterization of the defined compounds 1 and 2 was carried out by NMR‐ rsp. mass‐spectrometry and by crystal X‐ray analysis of 2 .     

Dodecaindane (tBu3Si)8In12—A Compound with an In12 Deltapolyhedron Framework

A unique feature among polyhedron frameworks of boron group elements is exhibited by the In₁₂ framework of the black-violet dodecaindane R^*₈In₁₂ (R*=SitBu₃), which can be obtained by the thermolysis of R^*₂In−InR^*₂. The molecular structure of R^*₈In₁₂ (tBu groups omitted in picture shown) can be described as a combination of two R^*₄In₆ octahedral building blocks and can thus be classified as a conjuncto dodecaindane.     

Hexasupersilyl-triprismo-hexastannane (tBu3Si)6Sn6—The First Molecular Tin Compound Containing a Sn6 Prism

Dark violet hexastannane ( t Bu ₃ Si) ₆ Sn ₆ displays a new framework motif for molecular tin compounds, in which six Sn atoms are located at the corners of a trigonal prism. The compound can be synthesized according to Equation (a). R*=SitBu₃.     

Comparative studies for selective deprotection of the N-arylideneamino moiety from heterocyclic amides: kinetic and theoretical studies

The kinetics, product analysis and theoretical studies for selective deprotection of N-arylideneamino pyridone, pyrimidinone and triazinone systems were carried out. Their reactivities were compared with each other and with related compounds previously studied. This reaction represents an efficient, clean and general synthetic procedure for the protection and selective synthesis of potential biologically active pyridines, pyrimidines and triazines and their derivatives.     

Anchimeric assistance by γ-substituents Z, Z=MeO, PhO, MeS or PhS, in reactions of the bromides (Me3Si)2(ZMe2Si)CSiMe2Br with AgBF4

The new organosilicon bromides (Me₃Si)₂(ZMe₂Si)CSiMe₂Br with Z=PhO or MeS have been prepared and new spectroscopic data obtained for the previously reported compounds with Z=H, F, Br, Me, Ph, MeO or PhS. Competitions between pairs of bromides for a deficiency of AgBF₄ in Et₂O, with the determination of the ratio of the fluoride products by ¹⁹F-NMR spectroscopy, have led to the following approximate relative reactivities of the bromides and so to the relative abilities of the γ-Z groups to provide anchimeric assistance to the leaving of Br⁻ in this reaction: Me, 1; Ph, 40; PhO, 3400; PhS, 5000; MeS, 7000; MeO, 54 000. In methanolysis in CH₂Cl₂, (Me₃Si)₂(MeOMe₂Si)CSiMe₂Cl has been found to be roughly 120 times as reactive as (Me₃Si)₂(PhOMe₂Si)CSiMe₂Cl. Combination of the results with previously available information suggests the following approximate order of ability of γ-groups Z to provide anchimeric assistance in reactions at the Si---X bonds in compounds (Me₃Si)₂(ZMe₂Si)CSiMe₂X: OCOMe>OMe>OCOCF₃>MeS>PhS, PhO>N₃, Cl>NCS>Ph>CH=CH₂>Me.     

Gas-phase NMR studies of chemical equilibria: 1—Methodology

Methods for obtaining ¹H NMR spectra of gases are discussed. Particular attention is paid to the nature of the tube and to the use of ‘second sample’ field/frequency locking. The question of the chemical shift reference is examined, and some results for tetramethylsilane gas are presented. Representative spectra are shown for three types of organic equilibria in the gas phase: keto-enol tautomerism, addition of methanol to acetaldehyde and Z-E isomerism of acetaldoxime.     

From the Lithium‐2‐anilide‐2‐fluoro‐1,3‐diaza‐2‐sila‐cyclopentene‐GaCl3 Adduct to 1,4,6‐Triaza‐5‐gallium‐7‐sila‐cyclo‐3‐heptene ‐ Experimental and Quantum‐chemical Results

The lithium salt (HC–NCMe₃)₂SiFNLiR ( 1 ) R = C₆H₃(2,6‐CHMe₂)₂ reacts with trichlorogallium under displacement of the lithium ion by GaCl₃ to give the adduct [(HC–NCMe₃)₂SiFN]^– [(GaCl₃)R·Li(thf)₄]⁺ ( 1 ). Compound 1 thermally loses LiCl and forms the bicyclic ring intermediates V and VI . Compound  VI adds the aniline H₂NC₆H₃(2,6‐CHMe₂)₂ and the unsaturated, seven‐membered ring compound –NCMe₃–CH₂–CH=NCMe₃GaCl₂–NR–SiFNHR– ( 2 ) is obtained. The addition is accompanied by an enamine‐imine‐tautomerism and proves the Lewis acid character of the silicon atom in an unknown 3‐center‐2‐electron interaction of one nitrogen atom with the silicon and gallium atoms. Quantum chemical calculations of the thermal isomerisation process and crystal structures of 1 and 2 are reported.     

[Me3Si(CF3)F]− and [Me3Si(CF3)2]−: Reactive Intermediates in Fluoride-Initiated Trifluoromethylation with Me3SiCF3— An NMR Study

The long-postulated reactive intermediates of polar fluoride-inititated trifluoromethylations with Me₃SiCF₃ (see scheme) were identified by NMR spectroscopy as [Me₃Si(CF₃)F]⁻ and [Me₃Si(CF₃)₂]⁻_.     

Synthesis, resolution and racemisation studies of new tridentate ligands for asymmetric catalysis

A method for the high-yielding preparation of two tridentate, isoquinoline-derived ligands, involving successive Suzuki cross-coupling reactions, is described. The first ligand could be resolved via molecular complexation with N-benzylcinchonidinium chloride, while the second was resolved by chromatographic separation of its epimeric camphorsulfonates. The barrier to rotation about the central biaryl axis was evaluated via racemisation studies, and the absolute configuration assigned by X-ray crystallography.     

Das Hexagallan [Ga6{SiMe(SiMe3)2}6] und das closo‐Hexagallanat [Ga6{Si(CMe3)3}4(CH2C6H5)2]2— — der Übergang zu einem ungewöhnlichen precloso‐Cluster

The Hexagallane [Ga₆{SiMe(SiMe₃)₂}₆] and the closo‐Hexagallanate [Ga₆{Si(CMe₃)₃}₄ (CH₂C₆H₅)₂]^2— — the Transition to an Unusual precloso‐Cluster The closo hexagallanate [Ga₆R₄(CH₂Ph)₂]^2— (R = Si^tBu₃) as well as the hexagallane Ga₆R₆ (R = SiMe(SiMe₃)₂) with only six cluster electron pairs were isolated from reactions of “GaI” with the corresponding silanides. The structure of the latter is derived from an octahedron by a Jahn‐Teller‐distortion and is different from the capped trigonal bipyramidal one expected by the Wade‐Mingos rules. Both compounds were characterized by X‐ray crystallography. The bonding is discussed with simplified Ga₆H₆ and Ga₆H₆^2— models via DFT methods.     

Diiodotetrasupersilylcyclotetrasilene (tBu3Si)4Si4I2—A Molecule Containing an Unsaturated Si4 Ring

The red-orange tetrasilacyclobutene 1 (R*=SitBu₃) is formed quantitatively by the reaction of tetrasilatetrahedrane 2 and iodine. Surprisingly, water and methanol do not react with 1 with addition to the Si−Si double bond, but instead with replacement of the silicon-bound iodine atoms with oxygen or the methoxy group, respectively. The substitutions possibly proceed by dissociative activation via intermediate 3 .     

Synthesis and Structure of a 1,4‐Dihydrazinotetrasilane

The reaction of hexakis(2,4,6‐triisopropylphenyl)tetrasilabuta‐1,3‐diene with anhydrous hydrazine furnishes the correspondingly substituted 1,4‐dihydrazinotetrasilane 2 . The X‐ray structure analysis of 2 reveals that the compound crystallizes as a conglomerate of enantiomerically pure crystals.     

Ce16Si15O6N32—An Oxonitridosilicate with Silicon Octahedrally Coordinated by Nitrogen

A rarity in solid‐state chemistry is octahedrally coordinated silicon. Ce₁₆Si₁₅O₆N₃₂ is the first nitridosilicate with this structural motif. Most oxosilicates containing octahedrally coordinated silicon are high‐pressure phases. In contrast to that Ce₁₆Si₁₅O₆N₃₂ has been synthesized under ambient pressure. An SiN₆ octahedron that is surrounded by two parallel rings formed from six Si(O,N)₄ tetrahedra is depicted.