Die chemie der schweren carben-analogen R2M,M = Si,Ge, Sn: IX. Eigenschaften und thermolyse von neuen 7-silabicyclo[2.2.1]heptadienen

Factors governing the ease and mechanism of 7-silabicyclo[2.2.1]heptadienes thermolysis in order to generate free silylenes and the corresponding benzene derivatives are investigated. For this purpose, 29 new compounds of the types VII–X have been prepared. No indications for a polar mechanism or an intermediate biradical could be found. The degradation is exactly of first order in all cases investigated sofar, and is enhanced by phenyl groups at the bridgehead C atoms, if a conformation coplanar with the basic ring is allowed by the neighbouring substituents, but is not enhanced by phenyl groups at the Si. The X-ray structure of two typical derivatives is discussed with this respect. A special mechanism is operating in the easy thermolysis of carbomethoxy-substituted compounds leading to cyclic sila enolether intermediates.     

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.     

通过核独立化学位移(NICS)计算研究二价三、五、七元环C2H2M, C4H4M and C6H6M(M=C, Si, Ge, Sn and Pb)的芳香族特性

The aromatic character of divalent three, five and seven-membered rings C₂H₂M, C₄H₄M and C₆H₆M(M=C, Si, Ge, Sn and Pb) is investigated through magnetic and geometric criteria by Density Functional Theory (DFT)method using 6^-311++G(3df,2p) basis set of the GAUSSIAN 98 program. The result of Nucleus-independent Chemical Shifts (NICS)(0.5) calculations show an aromatic character for singlet state of C₂H₂M(M=C, Si, Ge, Sn and Sn) and nonaromatic character for triplet states of C₂H₂M(except M=Ge and Pb). NICS (0.5) calculations show nonaromatic character for the singlet state of C₄H₄C and antiaromatic character for C₄H₄M(M=Si, Ge, Sn and Pb). In contrast, NICS (0.5) calculations indicate antiaromatic character for the triplet state of C₄H₄C and nonaromatic character to C₄H₄M(M=Si, Ge, Sn and Pb). NICS (0.5) calculations show a slightly homoaromatic character for the singlet state of C₆H₆M and anti-aromatic character for triplet state of C₆H₆M.     

Electronic Structure and Formation Heat of Pu3M and PuM3 (M=Ga, In, Sn and Ge) Compounds

The equilibrium structure, electronic structure, and formation heat of Pu₃M (PuM₃) (M=Ga, In, Sn, and Ge) compounds with AuCu₃ structure have been calculated using full potential linear augmented plane wave (FPLAPW) method within generalized-gradient approximation (GGA) including spin-orbit coupling (SOC) and spin polarization (SP). The calculated lattice parameters are in good agreement with the experimental values. Density of state analysis shows hybridization effects between Pu and M are governed by the competitions depending on the M amount: Pu 6d-Pu 5f, M p-Pu 6d, and M sp-M sp interactions. Electronegativity difference and electronic hybridization effect are two important factors to influence the formation heat and stability of Pu₃M (PuM₃) compounds. The larger is the electronegativity difference and the lower is M s-band or p-band center relative to the Fermi energy, the more negative is the formation heat and the more stable are Pu₃M (PuM₃) compounds.     

Etude théorique par la méthode DFT des structures non-classiques des systèmes X2H2F2 (X=Si, Ge, Sn)

The structure and the relative stability of isomers of molecules X₂H₂F₂ (X=Si, Ge, Sn) have been studied using the density functional theory (DFT). We have determined the optimised structures of the substituted isomers. The XX bond have been studied and compared to that of the parent molecules: X₂H₄. It appears that, for the planar and trans ethylenic systems, the double bond character of the XX decreases when the hydrogen atoms are substituted by fluorine atoms. The most stable structure is shown to be the one where the two fluorine atoms are fixed on the same atom. The bridged structures are also studied.     

Zur Kenntnis der inversen Perowskite M3TO (M = Ca,Sr, Yb; T = Si,Ge, Sn,Pb)

On the Inverse Perovskites M₃TO (M = Ca, Sr, Yb; T = Si, Ge, Sn, Pb) Ca₃SiO and seven further inverse perovskites M₃TO (M = Ca, Sr, Yb; T = Si, Ge, Sn, Pb) were prepared in iron crucibles under argon by the reactions 6 M + TO₂ + T = 2 M₃TO, and 3 M+ TO = M₃TO for Yb₃PbO, respectively, at temperatures between 1123 to 1173 K. The crystal structures of all compounds were solved and refined using X—ray powder diffraction methods. Ca₃SiO, Ca₃GeO, Sr₃SiO, Sr₃GeO, Yb₃SiO and Yb₃GeO are orthorhombic perovskites (anti—GdFeO₃—type, space group Pbnm, No. 62, Z = 4). They show slightly distorted corner—sharing OM₆ octahedra that are tilted with respect to their positions in the ideal perovskite structure. The effective radii of the T^4— vary significantly with M²⁺. Thus, these perovskites can no longer be discussed in terms of the hard—sphere model, and Goldschmidt's tolerance factor does not apply. The ideal cubic representatives Yb₃SnO and Yb₃PbO were refined in space group Pm3¯m (anti—SrTiO₃ type, Z = 1).     

Darstellung und charakterisierung von verbindungen des typs (CH3)3ME(CF3)2 (M = Si,Ge, Sn; E = P,As)

Various preparative routes for the synthesis of (CH₃)₃SiP(CF₃)₂ are discussed. The most favourable method, reaction of (CH₃)₃MPH₂ with HE(CF₃)₂, provides a good yield of (CH₃)₃ME(CF₃)₂ compounds (M = Si, Ge, Sn; E = P, As). The reaction rate is dependent on M (Si < Ge <Sn) und E (P < As). The stability and reactivity of the (CH₃)₃ME(CF₃)₂ compounds are discussed. The new compounds were characterized by NMR and IR spectra and by cleavage reactions of the M-E bond. ¹H, ¹⁹F NMR and IR spectral data are reported.     

The reflectivity spectra of ZnXP2 (X=Si, Ge, and Sn) compounds

Full Potential Augmented Plane Wave plus local orbital method ( FAPW+lo) calculations were performed for ZnSiP₂, ZnGeP₂, and ZnSnP₂ in the chalcopyrite structure in order to investigate the optical properties and to show the origin of the different optical transitions and their correspondence in the band structure. It is found that the most important features of the band gap is pseudo-direct for ZnSiP₂, indirect for ZnGeP₂, and direct for ZnSnP₂. Then the contribution of the different transitions peaks are analyzed from the imaginary part of the dielectric function and the reflectivity spectra.     

Bicyclo[2.2.2]octanes HC(SiMe2E)3MR (E=S, Se; M=Si, Ge, Sn; R=Me, Ph, Vi)

The reactions of 1:1 mixtures of the trisilylmethane HC(SiMe₂Cl)₃ (1b) and organo Group 14 trichlorides (RMCl₃, R=Me, Ph, vinyl (Vi); M=Si, Ge, Sn) with Li₂E (E=S, Se) in THF yielded the new bicyclo[2.2.2]octanes HC(SiMe₂E)₃MR (2a-6b). The products were identified by GC-MS and multinuclear NMR spectroscopy. Trends of the NMR data are discussed. The molecular structures of HC(SiMe₂S)₃SiMe (2a), HC(SiMe₂S)₃SiPh (3a), HC(SiMe₂Se)₃SiVi (4b) and HC(SiMe₂Se)₃GeMe (5b) are reported.     

Vibrational assignment of some X3MCo(CO)4 molecules (M = Si,Ge, Sn and X = Cl,Br, I)

The infrared and Raman vibrational spectra of X₃MCo(CO)₄ compounds (M = Si, Ge, Sn and X = Cl, Br, I) including depolarization measurements are presented. These spectra result in complete vibrational assignments which are different from those reported previously.     

Low coordinate germanium and tin compounds (ArO)2ME and (ArO)2MM′Ln M=Ge, Sn; E=S, Se, –NSiMe3 M′=Cr, W, Fe, Pt [Ar=2,4,6-tris((dimethylamino)methyl)phenyl-]

The reactions of the divalent species (ArO)₂M (Ar=2,4,6-[(CH₃)₂NCH₂]₃C₆H₂; M=Ge, Sn) with either Me₃SiN₃, elemental S₈, Se or transition metal complexes M′(CO)_n+1 (M′=Fe, n=4; M′=Cr, W; n=5) (Ph₃P)₂Pt·C₂H₄ have resulted in the isolation of either the new stable formal metallanimines (ArO)₂M=N–SiMe₃, germanethione, -selone (ArO)₂Ge=E (E=S, Se) (the expected formations of the stannanethione and -selone were not observed), or the (ArO)₂M=M′(CO)_n, (ArO)₂M=Pt(PPh₃)₂ complexes, respectively. The direct oxidation of the (ArO)₂M species with various oxidizing agents led to the formation of the corresponding metalloxanes [(ArO)₂M–O–]₂. All of the chalcogenido- and transition metal–metal 14 complexes have been physicochemically and chemically characterized. The reactions of the (ArO)₂Ge=E (E=S, Se) compounds with 3,5-di-tert-butyl-1,2-benzoquinone produced, by extrusion of sulfur or selenium, the dioxametalloles corresponding to the formal addition of the divalent species (ArO)₂M to the benzoquinone. A substitution reaction of chalcogen (S/Se) has been observed permitting to go from germaneselone to germanethione.     

Protolyses of (CH3)3SnM(CH3)3 (M = Sn,Ge, Si,C)

Product and kinetic studies on the reactions of hydrogen chloride in methanol solution with the substrates (CH₃)₃SnM(CH₃)₃ (M = Sn; Ge and Si) show that both SnM and SnCH₃ cleavage reactions occur, at similar rates, and are followed by other reactions giving complex but explicable mixtures of products. Similar behaviour is observed for trifluoroacetolysis in carbon tetrachloride solution, and some intermediates are observable. Trifluoroacetolysis of (CH₃)₃SnC(CH₃)₃ results in exclusive SnCH₃ cleavage. The very slow apparent solvolysis in acetic acid solution is thought to involve reaction with dissolved oxygen.     

Electric birefringences and solution-state conformations of molecules C6H5SM(CH3)3 ; M = C,Si, Ge or Sn

Dipole moment and electric birefringence studies are reported for the series of molecules C₆H₅SM(CH₃)₃ in cyclohexane solution; M = C, Si, Ge or Sn. The experimental data are analysed to determine the preferred solution-state conformations. The dihedral angles between the C₆H₅ and C_arSM planes are, in turn, 82 ± 11°, 80 ± 11°, 66 ± 12° and 46 ± 10°.     

Metallorganische verbindungen des 1,2-diethinylbenzols vom typ o-C6H4(CCMR3)2 (M = Si,Ge, Pb)

The preparation of the compounds o-C₆H₄(CCMR₃)₂ (M = Si, Ge, Pb; R = CH₃; M = Pb; R = C₆H₅) is described. Their properties are compared with those of o-C₆H₄(CCSnR₃)₂ (R = CH₃, C₆H₅) and those of their p-isomers. The structures and bonding conditions proposed for these molecules are supported by dipole measurements, mass spectroscopy, IR, Raman, ¹H NMR and ¹³C NMR data.     

Syntheses of MO2 (M=Si, Ce, Sn) nanoparticles by solid-state reactions at ambient temperature

Nano oxides (SiO₂, CeO₂, SnO₂) were successfully synthesized by solid-state reactions at ambient temperature. The nanoparticles were characterized by X-ray powder diffraction, TEM, BET, and TGA-DTA. The SiO₂ particles were also investigated using IR spectra. Effects of calcination on the nanoparticles were studied in this paper. The solid-state reaction technique is a convenient, inexpensive and an effective preparation method of monodisperse oxide nanoparticles in high yield. The mechanisms of the formation of nano materials by solid-state reactions at ambient temperature were primarily investigated.     

Electronic structure and vibrational spectra of X20H20 (X=C, Si, Ge, Sn): A theoretical study

Optimized geometries, HOMO–LUMO gaps, vertical ionization potentials and electron affinities are obtained using HF, and B3LYP methods with 6-311G** basis set for C₂₀H₂₀, Si₂₀H₂₀ and Ge₂₀H₂₀. For germanium and tin analogues, B3LYP calculations are performed with LANL2DZ effective core potential. Electron correlation is included by doing MP2 calculation. The harmonic frequencies of all the compounds are obtained using B3LYP with 6-311G** and/or LANL2DZ basis sets. The force field and vibrational spectra are analyzed and 74 symmetry unique non-redundant local force constants are evaluated. Probable assignments are proposed for all the fundamentals based on the potential energy distribution.     

Eine gewichtsanalytische Methode zur Bestimmung des Magnesiums als MgNH4AsO4.6H2O

Ohne Zusammenfassung     

Modellrechnungen von Kraftkonstanten der Tetramethyl-Verbindungen (CH3)4−nM(CD3) n,M=Si,Ge, Sn,Pb

Fromthe experiemntal fundamental vibrational frequencies of (CH₃)₄ M, (CD₃)₄ M and (CH₃)₃ MCD₃,M=Si, Ge, Sn, Pb, and of (CH₃)₂Si(CD₃)₂ and CH₃Si(CD₃)₃ a transferable local symmetry type force field for (CH₃)_4–n M groups has been calculated. Applications involving differentM atoms and numbersn of CH₃ groups are presented.

     

PW_(11)M(M=Cu、 Co)@TiO_2多相催化剂的制备及氧化脱硫性能

以过渡金属(Cu, Co)取代磷钨酸为模板剂,硫酸钛为钛源,通过一步模板法合成出一类多酸基PW_(11)M(M=Cu、 Co)@TiO_2材料,采用FT-IR、 XRD、 XPS、 Raman、 SEM和TEM表征手段对材料进行了结构表征.结果表明, PW_(11)M(M=Cu、 Co)被引入到TiO_2中,形成了球形核壳结构. N_2吸附-脱附测试表明, PW_(11)Co@TiO_2具有介孔结构:孔径大小为3.3 nm,比表面积为72.4 m~2/g.在以H_2O_2为氧化剂,乙腈为溶剂的氧化脱硫反应体系中考察了其催化活性,结果表明:复合材料PW_(11)M(M=Cu、 Co)@TiO_2表现出良好的催化性能.其中催化剂PW_(11)Co@TiO_2在投入量为40 mg,反应底物为500 ppm,反应温度60℃,反应40 min后, DBT的脱硫率达到99.7%.中断和循环实验表明,催化剂PW_(11)Co@TiO_2具有良好的稳定性,在相同的反应条件下,循环反应5次后,催化剂的催化活性没有明显下降.