Reactions of bis(trimethylsilyl)amine and -amide with MoOCl4

Oxo-Mo(VI) imido-chloride, [MoOCl₂(NH)(Et ₂O)] _n and nitrido-chloride, [Mo₂O₂Cl₂(N)₂(Et ₂O)] _n have been synthesized by equimolar reactions of MoOCl₄ with HN(SiMe ₃)₂ and LiN(SiMe ₃)₂, respectively. Higher molar reactions of HN(SiMe ₃)₂ lead to imido-silylamido derivatives, [Mo₂OCl₃(NH)₃(NHSiMe ₃)] _n , whereas those of LiN(SiMe ₃)₂ give silylimido bridged compounds, Mo₄O₄Cl₄(NSiMe ₃)₆ and Mo₄O₄(NSiMe ₃)₈. Elemental analyses, redox titration, magnetic moment, molecular weight, molar conductance, infrared,¹H-NMR and TG-DTG-DTA studies are reported.

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Reaktionen von Bis(trimethylsilyl)amin und -amid mit MoOCl₄

Zusammenfassung Durch equimolare Reaktionen von MoOCl₄ mit HN(SiMe ₃)₂ und LiN(SiMe ₃)₂ wurden die Oxo-Mo(VI) Imido-chloride [MoOCl₂(NH)(Et ₂O)] _n und die Nitrido-chloride [Mo₂O₂Cl₂(N)₂(Et ₂O)] _n dargestellt. Höhermolekulare Reaktionen von HN(SiMe ₃)₂ führen zu Imido-silylamido Derivaten [Mo₂OCl₃(NH)₃(NHSiMe ₃)] _n , währenddessen die von LiN(SiMe ₃)₂ silylimidoüberbrückte Verbindungen ergeben: Mo₄O₄Cl₄(NSiMe ₃)₆ und Mo₄O₄(NSiMe ₃)₈. Die Strukturen sind mit Elementaranalysen, Redoxtitrationen, Messung der magnetischen Momente, Molekulargewichten, molarer Leitfähigkeit, Infrarot,¹H-NMR und TG-DTG-DTA-Untersuchungen charakterisiert.

     

Zur Reaktion von Permethylcyclosilanen mit Halogenen

The series of ,-diiodopermethylpolysilanes, I(SiMe ₂) _n I, (n=4–6) andX(SiMe ₂)₄ X, (X=Cl, Br) has been prepared by the action of halogen on the corresponding cyclic compounds (SiMe ₂) _n . The mass spectra, NMR-, IR- andRaman-spectra of these compounds have been recorded.

Herrn Prof. Dr.Josef Schurz zum 60. Geburtstag gewidmet.     

Beiträge zur chemie der halogensilan-addukte XV. 2,2′-bipyridin- und 1,10-phenanthrolin-komplexe von halogendisilanen und Si3Cl8

A series of mono-bipy and -phen complexes (bipy = bipyridine, phen = phenanthroline) of the perhalodisilanes, Si₂F₆, Si₂Cl₆ and Si₂Br₆, mixed methylhalodisilanes (Si₂Me_nX_6?n, X = Cl, I; n = 2,3) and Si₃Cl₈ · bipy have been prepared by reaction of the components, and have been characterized. $\text{1}\text{1}$ complexes are obtained exclusively.The structures of all complexes involve coordination of the base to the more acidic silicon and perpendicular alignment of the SiSi axis on the plane of the ligand. This may be rationalised in terms of steric requirements of the different groups, the more demanding groups occupying the sterically more favorable positions vertical to the plane of the ligand. For Si₃Cl₈ · bipy, spectroscopic and chemical evidence suggests bipy-coordination to the center silicon. PMR investigations of the dissociation equilibria of the complexes in solution led to determination of the heats of formation of four of the complexes and to a qualitative estimation of the relative acceptor strengths of several disilanes. Contrary to expectation, silyl groups increase the acceptor strength of silicon considerably and in the order SiMe₃ < SiMe₂Cl < SiMeCl₂ < SiCl₃. The effect of a SiMe₃, substituent group may be compared to that of Cl. Methylchlorosilyl groups may exceed the effect of Cl as indicated by the increase in acceptor strength in the sequence (R =) Me < Ci < SiMe₂Cl < SiMeCl₂ for the acceptor RSiCl₂Me. Si₃Cl₈ is the strongest acceptor in the series. Assuming the structural suggestion for Si₃Cl₈ · bipy (center coordination) to be correct an increase in acceptor strength is indicated in the sequence SiCl₃(Si₂Cl₅) < SiCl₂(SiCl₃)₂ (Si = coordinating center). This may be interpreted mainly in terms of charge accepting capacity of the polarisable silyl groups. Another interesting sequence of acceptor strengths measured in this work is 1,1,2-Si₂Me₃F₃, 1,2-Si₂Me₂F₄ < Si₂Me₃Cl₃ < 1,2-Si₂Me₂Cl₄, showing fluorodisilanes to be weaker acceptors than chlorodisilanes. This result is compared to the heats of formation of SiX₄ · 2py complexes.     

Synthese und Kernresonanzspektren von Methylphenyl-substituierten Trisilylphosphanen PSi3 Me n Ph 9−n

Trisilylphosphanes of the type PSi₃ Me _x Ph _9–x are formed when sodium/potassiumphosphide reacts with methylphenylchlorosilanesMe _n Ph _3–n SiCl or with mixtures of methylphenylchlorosilanes. The phosphanes (SiMe ₃) _n P (SiMe _m Ph _3–m )_3–n (n, m=0, 1, 2, 3) were separated and purified by destillation or crystallization and their²⁹Si as well as³¹P-NMR-spectra were recorded.

     

The vibrational spectra of linear and branched perchlorosilanes Si n Cl2n+2 and their simulation using a local symmetry force field

Infrared andRaman vibrational spectra ofn-Si₄Cl₁₀,n-Si₅Cl₁₂,neo-Si₅Cl₁₂ and [(SiCl₃)₃Si]₂ have been measured and assigned. A local symmetry force field has been developed to simulate vibrational spectra of all (noncyclic) perchlorosilanes Si _n Cl_2n+2 known today (n=2, 3, 4, 5, 8). The observed spectra are reproduced satisfactorily

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Die Vibrationsspektren linearer und verzweigter PerchlorsilaneSi _n Cl _2n+2 und deren Simulierung mittels eines lokalen Symmetrie-Kraftfeldes

Zusammenfassung Infrarot- undRaman-Spektren vonn-Si₄Cl₁₀,n-Si₅Cl₁₂,neo-Si₅Cl₁₂ und [(SiCl₃)₃Si]₂ wurden aufgenommen und zugeordnet. Ein lokales Symmetrie-Kraftfeld zur Simulation der Spektren aller bisher bekannten (nicht cyclischen) Perchlorsilane Si _n Cl_2n+2 (n=2, 3, 4, 5, 8) wird angegeben. Die beobachteten Spektren werden zufriedenstellend reproduziert

     

Herstellung von Tetrahydrofuranverbindungen der Seltenerdbromide

Zusammenfassung Die wasserfr. Bromide der Lanthanide einschließlich LaBr₃ und YBr₃ wurden nach der Ammonbromid-Vakuummethode hergestellt und ihr Oxidbromidgehalt untersucht. Beim Europium entstand EuBr₂, das bei Raumtemp. gegen Br₂ stabil ist, in Gegenwart von Tetrahydrofuran (THF) jedoch leicht oxydiert wird. DieTHF-Verbindungen der Erdbromide wurden dargestellt; sie haben die ZusammensetzungMeBr₃·4THF (Me=La, Ce, Pr),MeBr₃·3,5THF (Me=Nd bis Er einschließlich Y) undMeBr₃·3THF (Me=Tm, Yb, Lu). Die Löslichkeit inTHF wurde bestimmt. Durch die extraktive Überführung in dieTHF-Verbindungen können die Seltenerdbromide vom Oxidbromid vollständig befreit werden.

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The anhydrous bromides of the lanthanides including LaBr₃ and YBr₃ were prepared by the ammonium bromide-vacuummethod and their content of oxide bromide studied. For Europium there resulted EuBr₂, which was stable against Br₂ at room temperature, but was easily oxidised in the presence of tetrahydrofurane (THF). TheTHF-compounds of the rare earth bromides were prepared; their compositions areMeBr₃·4THF (Me=La, Ce, Pr),MeBr₃·3,5THF (Me=Nd to Er including Y) andMeBr₃·3THF (Me=Tm, Yb, Lu). The solubility inTHF was determined. The rare earth bromides can be completely freed from oxide bromide by extractive convertion to theTHF-compounds.

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Mit 1 Abbildung     

Darstellung,Strukturen und EPR-Spektren der Rhenium(II)Thionitrosylkomplexe trans-[Re(NS)Cl3(MePh2P)2] und trans-[Re(NS)Br3(Me2PhP)2]

Preparation, Structures, and EPR Spectra of the Rhenium(II) Thionitrosyl Complexes trans -[Re(NS)Cl₃(MePh₂P)₂] and trans -[Re(NS)Br₃(Me₂PhP)₂] The paramagnetic rhenium(II) thionitrosyl compounds trans-[Re(NS)Cl₃(MePh₂P)₂] and trans-[Re(NS)Br₃(Me₂PhP)₂] are characterized by crystal structure diffraction and EPR spectroscopy. Trans-[Re(NS)Cl₃(MePh₂P)₂] is formed during the reduction of (a) [ReNCl₂(MePh₂P)₃] with disulphur dichloride or (b) of mer-[ReCl₃(MePh₂P)₃] with trithiazyl chloride. Trans-[Re(NS)Br₃(Me₂PhP)₂] is the final product of the ligand exchange reaction of mer-[Re(NS)Cl₂(Me₂PhP)₃] with bromine whereby the metal occurred to be simultaneusly oxidized. The crystal structure analyses show for trans-[Re(NS)Cl₃(MePh₂P)₂] (monoclinic, C2/c, a = 13.831(3) Å, b = 13.970(1) Å, c = 14.682(2) Å, β = 95.33(1), Z = 4) and trans-[Re(NS)Br₃(Me₂PhP)₂] (monoclinic, C2/c, a = 33.292(5) Å, b = 8.697(1) Å, c = 17.495(3) Å, β = 115.65(1), Z = 8) linear co-ordinated NS ligands (Re–N–S-angles 180° and 174.8°). The metal atom is octahedrally co-ordinated with the phosphine ligands in trans position to each other. X-band and Q-band EPR spectra of the rhenium(II) thionitrosyl complexes (5 d⁵ “low-spin” configuration, S = 1/2) are detected in the temperature range 295 ≥ T ≥ 130 K. They are characterized by well resolved ^185,187Re hyperfine patterns. The hyperfine parameters are used to get information about the spin-density distribution of the unpaired electron in the complexes under study.     

Making Use of the Direct Process Residue: Synthesis of Bifunctional Monosilanes

The industrial production of monosilanes Me_nSiCl_4−n (n=1–3) through the Müller–Rochow Direct Process generates disilanes Me_nSi₂Cl_6−n (n=2–6) as unwanted byproducts (“Direct Process Residue”, DPR) by the thousands of tons annually, large quantities of which are usually disposed of by incineration. Herein we report a surprisingly facile and highly effective protocol for conversion of the DPR: hydrogenation with complex metal hydrides followed by Si−Si bond cleavage with HCl/ether solutions gives (mostly bifunctional) monosilanes in excellent yields. Competing side reactions are efficiently suppressed by the appropriate choice of reaction conditions.     

Darstellung und Schwingungsspektren von Chloro-Bromo-Dirhodaten(III), [Rh2ClnBr9−n]3−, n = 0–9

Preparation and Vibrational Spectra of Nonahalogenodirhodates(III), [Rh₂Cl_nBr_9-n]^3?, n = 0–9 The pure nonahalogenodirhodates(III), A₃[Rh₂Cl_nBr_9-n], A = K, Cs, (TBA); n = 0–4, 9, have been prepared. They are formed from the monomer chlorobromorhodates(III), [RhCl_nBr_6-n]^3?, n = 0–6, which are bridged to confacial bioctahedral complexes by ligand abstraction in less polar organic solvents. From the mixtures the complexions are separated by ion exchange chromatography on DEAE-cellulose. The solid, air-stable, air-stable, K-, Cs- and (TBA)-salts of [Rh₂Cl_nBr_9-n]^3?, n = 0–4, are green, of [Rh₂Cl₉]^3? are brown. The IR and Raman spectra of [Rh₂Br₉]^3? and [Rh₂Cl₉]^3? are assigned according to the point group D_3h. The chlorobromodirhodates exist as mixtures of geometrical and structural isomers, which belong to different point groups. The vibrational spectra exhibit bands in characteristic regions; at high wavenumbers stretching vibrations with terminal ligands v(Rh—Cl_t): 360–320, v(Rh—Br_t): 280–250; in a middle region with bridging ligands v(Rh—Cl_b): 300–270, v(Rh—Br_b): 210–170 cm^?1; the deformation bands are observed at distinct lower frequencies. The terminal ligands are fixed very strong, and the distance between v(Rh—X_t) and v(Rh—X_b) increases with decreasing size of the cations.     

Fragmentation behavior of Si2Cln+ cations (n = 1—6)

Sector-field mass spectrometry was used to probe the fragmentation patterns of the cationic silicon chlorides Si₂Cl_n ⁺ (n = 1—6). For almost all Si₂Cl_n ⁺ ions, Si—Si fragmentation predominates the Si—Cl bond cleavage both in the metastable ion and collisional activation mass spectra. Analysis of the fragmentation patterns indicates that the long-lived radical cation Si₂Cl₆ ^·+ corresponds to a complex [SiCl₂·SiCl₄]^·+ rather than the intact molecular ion of hexachlorodisilane. The behavior of Si₂Cl₅ ⁺ is consistent with the formation of the (trichlorosilyl)dichlorosilyl cation Cl₃SiSICl₂ ⁺. Structural aspects are also discussed for the other Si₂Cl_n ⁺ species. A semi-quantitative analysis of the fragmentation patterns in conjunction with the literature thermochemistry data was used to estimate some thermochemical properties of the Si₂Cl_n ⁺ cations.     

Study of temperature effect on uni-univalent and uni-bivalent ion exchange reaction

Ion exchange equilibrium constant (K) for Cl⁻/Br⁻ and Cl⁻/C₂O₄²⁻ system was studied at different temperatures from 30 to 45°C. For both uni-univalent and uni-bivalent exchange systems, the value of K increases with rise in temperature i.e., from 1.16 at 30°C to 2.95 at 45°C for Cl⁻/Br⁻ system and 19.5 at 30°C to 30.0 at 45°C for Cl⁻/C₂O₄²⁻ system indicating the endothermic ion exchange reaction. The difference in K values at the same temperature for the two was related to the ionic charge of exchangeable ions in the solution. The article is published in the original.     

Investigation of the electronic structures of vinyl silicon compounds by the free electron method

The two compounds, Me₄Si₂ (C₂H₃)₂ and Me₈Si₂ (C₂H₃)₂ have been studied by the anti-symmetrized free electron molecular orbital method. Electron delocalisation over the whole chain via the silicon atoms occurs and a satisfactory account of the electronic spectra may be obtained.

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Zusammenfassung Me₄Si₂ (C₂H₃)₂ und Me₈Si₄ (C₂H₃)₂ wurden nach der MO-Methode des freien Elektronengases behandelt. Delokalisierung der Elektronen über die Si-Atome der Kette wird festgestellt. Die berechneten Spektren sind zufriedenstellend.

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Résumé On a étudié par la méthode des orbitales moléculaires d'électrons libres avec antisymétrisation les composés Me₄Si₂(C₂H₃)₂ et Me₈Si₄(C₂H₃)₂. Il se produit une délocalisation électronique le long de toute la chaÎne par l'intermédiaire des atomes de silicium, et l'on peut rendre compte d'une manière satisfaisante des spectres électroniques.

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We wish to thank the S.R.C. for a maintenance grant to one of us (D.R.A.).     

2D Oligosilyl Metal–Organic Frameworks as Multi‐state Switchable Materials

We report the synthesis of a set of 2D metal–organic frameworks (MOFs) constructed with organosilicon‐based linkers. These oligosilyl MOFs feature linear Si_nMe_2n(C₆H₄CO₂H)₂ ligands (lin‐Si_n, n=2, 4) connected by Cu paddlewheels. The stacking arrangement of the 2D sheets is dictated by van der Waals interactions and is tunable by solvent exchange, leading to reversible structural transformations between many crystalline and amorphous phases.     

Synthesis of α,ω-dihalopermethyloligosilanes and silane-siloxane copolymers

α,ω-Dibromopermethyloligosilanes, Br(SiMe₂) _n Br (n=2–4, 6), were prepared by the reaction of dodecamethylcyclohexasilane with bromine. The reaction of (Me₂Si)₆ with MCl₄ (M=Sn, Ti) proceeds with the cleavage of Si−Si- and Si−C-bonds with the formation of α,ω-dichloropermethyloligosilanes, Cl(SiMe₂) _n Cl (n=2–4, 6), and chloro derivatives of cyclohexasilane, Cl _m Si₆Me_12−m (m=1, 2). Silane-siloxane copolymers of regular structure were obtained by heterofunctional copolycondensation of α,ω-dihalopermethyloligosilanes with 1,5-dihydroxyhexamethyltrisiloxane. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1513–1517, August, 1997.     

Functionalization of one or two methyl groups in the [Cp*<Subscript>2</Subscript>RuBr]<Superscript>+</Superscript>Br<Superscript>−</Superscript> complex in the reaction with bromine

The reaction of [Cp*₂RuBr]⁺Br⁻ with bromine in CH₂Cl₂ (CD₂Cl₂) in an inert atmosphere at room temperature produces the complexes [Cp*Ru(Br)C₅Me₄CH₂Br]⁺Br₃ ⁻ (syn conformer), [Cp*Ru(Br)C₅Me₃(CH₂Br)₂]⁺ (syn and anti conformers), and [Ru(Br)(C₅Me₄CH₂Br)₂]⁺ (syn conformer). All complexes were characterized by ¹H and ¹³C NMR spectroscopy; the former complex, by elemental analysis. These complexes were also prepared by the reaction of [Cp*RuC₅Me₄CH₂]⁺BF₄ ⁻ with bromine in CH₂Cl₂. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2712–2718, December, 2005.     

Selective One-Pot Syntheses of Mixed Silicon-Germanium Heteroadamantane Clusters

Si_xGe_y alloys are emerging materials for modern semiconductor technology. Well-defined model systems of the bulk structures aid in understanding their intrinsic characteristics. Three such model clusters have now been realized in the form of the Si_xGe_y heteroadamantanes [0] , [1] , and [2] through selective one-pot syntheses starting from Me₂GeCl₂, Si₂Cl₆, and [nBu₄N]Cl. Compound [0] contains six GeMe₂ and four SiSiCl₃ vertices, whereas one and two of the GeMe₂ groups are replaced by SiCl₂ moieties in compounds [1] and [2] , respectively. Chloride-ion-mediated rearrangement quantitatively converts [2] into [1] at room temperature and finally into [0] at 60 °C, which is not only remarkable in view of the rigidity of these cage structures but also sheds light on the assembly mechanism.     

New Cyclic and Polycyclic Ring Systems Containing Group 14 (Si,Ge, Sn) and 16 (S,Se, Te) Elements

The reactions of Me₂MCl₂ (M = Si, Ge, Sn), Si₂Me₄Cl₂, Si₂Me₂Cl₃, Si₂Me₂Cl₄ and CH₂(SiCl₂Me)₂, and suitable mixtures thereof, with H₂S / NEt₃ and Li₂E (E = Se, Te) have been investigated and lead to a variety of new group 14 chalcogenide systems.     

Darstellung,Schwingungsspektren und Normalkoordinatenanalyse der Halogenonitrosylruthenate [Ru(NO)ClnBr5–n]2–, n = 0–5, sowie die Kristallstruktur von (CH2py2)[Ru(NO)ClBr4]

Syntheses, Vibrational Spectra, and Normal Coordinate Analysis of Halogenonitrosylruthenates [Ru(NO)Cl_nBr_5–n]^2–, n = 0–5, and the Crystal Structure of (CH₂py₂)[Ru(NO)ClBr₄] By treatment of [Ru(NO)Cl₅]^2– with anhydrous HBr in dichloromethane a mixture of [Ru(NO)Cl_nBr_5–n]^2–, n = 0–5, is formed, from which individual complexes can be separated by ion exchange chromatography on diethylaminoethyl cellulose. The X-Ray structure determination on a single crystal of (CH₂py₂)[Ru(NO)ClBr₄] (monoclinic, space group P2₁/c, a = 11.480(2), b = 10.175(4), c = 16.025(6) Å, β = 107.40(1)°, Z = 4) reveals, that the chlorine atom is trans positioned to the nitrosyl group. The low temperature IR and Raman spectra have been recorded of six complexes of the series (n-Bu₄N)₂[Ru(NO)Cl_nBr_5–n], n = 0–5, and are assigned by normal coordinate analysis. A good agreement between observed and calculated frequencies is achieved. The valence force constants are f_d(NO) = 13.86–13.93 und f_d(RuN) = 5.43–5.49 mdyn/Å.     

Synthesis of Functional Monosilanes by Disilane Cleavage with Phosphonium Chlorides

The Müller–Rochow direct process (DP) for the large-scale production of methylchlorosilanes Me_nSiCl_4−n (n=1–3) generates a disilane residue (Me_nSi₂Cl_6−n, n=1–6, DPR) in thousands of tons annually. This report is on methylchlorodisilane cleavage reactions with use of phosphonium chlorides as the cleavage catalysts and reaction partners to preferably obtain bifunctional monosilanes Me_xSiH_yCl_z (x=2, y=z=1; x,y=1, z=2; x=z=1, y=2). Product formation is controlled by the reaction temperature, the amount of phosphonium chloride employed, the choice of substituents at the phosphorus atom, and optionally by the presence of hydrogen chloride, dissolved in ethers, in the reaction mixture. Replacement of chloro by hydrido substituents at the disilane backbone strongly increases the overall efficiency of disilane cleavage, which allows nearly quantitative silane monomer formation under comparably moderate conditions. This efficient workup of the DPR thus not only increases the economic value of the DP, but also minimizes environmental pollution.     

Komplexbildung mit 1,2-bis (o-Aminobenzylidenamino)-ethan als neutralem Liganden

Compounds [Co(H₂ L]X ₂(X=Cl, Br, I, NO₃, ClO₄), [Co(H₂ L–Br₂)]Br₂, [Co(H₂ L–Br₂)·py ₂]Br₂ and [Co(H₂ L)Cl]Cl₂ were isolated. They were investigated by means of thermoanalysis, IR and VIS spectroscopy, magnetochemistry and molar conductivity.