Controlling the morphology, electronic properties, and growth direction of nanowires (NWs) is an important aspect regarding their integration into devices on technologically relevant scales. Using the vapor-solid-solid (VSS) approach, with Ni as a catalyst and octachlorotrisilane (Si(3)Cl(8), OCTS) as a precursor, we achieved epitaxial growth of rectangular-shaped Si-NWs, which may have important implications for electronic mobility and light scattering in NW devices. The process parameters were adjusted to form cubic α-NiSi(2) particles which further act as the shaping element leading to prismatic Si-NWs. Along with the uncommon shape, also different crystallographic growth directions, namely, [100] and [110], were observed on the very same sample. The growth orientations were determined by analysis of the NWs' azimuths on the Si (111) substrates as well as by detailed transmission electron microscopy (TEM) and selected area electron diffraction (SAED) investigations.

Es wird ein Verfahren zur Herstellung von Silicium hoher Reinheit beschrieben. Aus SiO2-haltigen Ausgangsstoffen wird durch Carbochlorierung SiCl4 hergestellt, aus dem in weiteren Verfahrensschritten das Silicium hoher Reinheit gewonnen wird. In samtlichen Verfahrensschritten wird kein elementares Silicium zugefuhrt. Auf diese Weise ergibt sich eine besonders effiziente und kostengunstige Verfahrensweise.

The applicability of a novel silicon precursor with respect to reasonable nanowire (NW) growth rates, feasibility of epitaxial NW growth and versatility with respect to diverse catalysts was investigated. Epitaxial growth of Si-NWs was achieved using octochlorotrisilane (OCTS) as Si precursor and Au as catalyst. In contrast to the synthesis approach with SiCl(4) as precursor, OCTS provides Si without the addition of H(2). By optimizing the growth conditions, effective NW synthesis is shown for alternative catalysts, in particular, Cu, Ag, Ni, and Pt with the latter two being compatible to complementary metal-oxide-semiconductor technology. As for these catalysts, the growth temperatures are lower than the lowest liquid eutectic; we suggest that the catalyst particle is in the solid state during NW growth and that a solid-phase diffusion process, either in the bulk, on the surface, or both, must be responsible for NW nucleation.

Es wird ein Verfahren zur Herstellung von hydriertem Polygerman als reine Verbindung oder Gemisch von Verbindungen, bei dem halogeniertes Polygerman hydriert wird, angegeben. Weiterhin werden ein hydriertes Polygerman sowie eine aus dem hydrierten Polygerman hergestellte Germaniumschicht und ein Verfahren zu ihrer Herstellung angegeben.

Halogenated polysilane as a pure compound or mixture of compounds each having at least a direct bond Si-Si whose substituents consist of halogen or of halogen and hydrogen, and in the composition thereof, the atomic ratio substituent: silicon is at least 1: 1, characterized in that a) The H content of the polysilane is less than 2 atomic%, b) the polysilane contains almost no short-chain branched chains and rings, wherein the content of branching points of the short-chain fraction based on the total product mixture amounts to <1%, c) it has a Raman molecular vibrational spectrum of I d) it has in

Molecules of the title compound, [Cu 4 Na 4 (C 6 H 5 O 2 Si) 12 (C 4 H 10 O) 8 ], are located on special positions of site symmetry \overline{4}. The Cu atoms are coordinated in a square planar fashion. The Na atoms, on the other hand, show an irregular sixfold coordination mode. The molecular conformation is stabilized by O—H...O hydrogen bonds.

The title compound, C19H15+.C48H60BF16Si4-, consists of discrete cations and anions. There are two ions of each kind in the asymmetric unit.

The title compound, C19H15+·C48H60BF16Si4−, consists of discrete cations and anions. There are two ions of each kind in the asymmetric unit.

Reaction of bis(cyclopentenemethyl)diethylplumbane (2) with trityl cation leads to the formation of the plumbyl cation bis(cyclopentenemethyl)plumbylium (1), in which the positively charged lead atom interacts with the two C=C double bonds of the cyclopentene ligands. The plumbyl cation 1 is characterized by NMR spectroscopy (delta((207)Pb)=807 ppm, delta((13)C(C=C))= 136.1 ppm, (1)J(Pb,C=C)=14.4 Hz) and X-ray crystallography. The structure of 1 reveals a distorted trigonal-bipyramidal coordination sphere for the lead atom with a unique coordination of two C=C double bonds in apical positions. According to quantum-mechanical calculations (MP2/6-311G(d,p) (C, H), SDD (Pb)//MP2/6-31G(d), SDD (Pb)) this interaction stabilizes 1 by 28.3 kcal mol(-1) relative to the tricoordinated plumbylium ion 10. An "atoms in molecules" (AIM) analysis indicates a pi-type interaction between the lead atom and the C=C double bonds, reminiscent of that in the 2-norbornyl cation.

Norbornyl cations of the group 14 elements Si --> Pb have been synthesized from substituted 3-cyclopentenemethyl precursors by intramolecular addition of transient cations to the C=C double bond of the 3-cyclopentenemethyl substituent (pi-route to norbornyl cations). The norbornyl cations 4a (E = Si, R = Me), 4e (E = Si, R = Et), 4f (E = Si, R = Bu), 4g (E = Ge, R = Bu), 4h (E = Sn, R = Bu), and 4i (E = Pb, R = Et) have been identified by their characteristic NMR chemical shifts (4a,e,f, delta((29)Si) = 80-87, delta((13)C)(CH=) = 149.6-150.6; 4g, delta((13)C)(CH=) = 144.8; 4h, delta((119)Sn) = 334, delta((13)C)(CH=) = 141.5; 4i, delta((207)Pb) = 1049, delta((13)C)(CH=) = 138). The significant deshielding of the vinylic carbon atoms (Deltadelta((13)C)) relative to those of the precursor (Deltadelta((13)C) = 19.3-20.3 (4a,e,f), Deltadelta((13)C) = 14.6 (4g), Deltadelta((13)C) = 11.1 (4h), Deltadelta((13)C) approximately 8 (4i)) and the small J coupling constants between the element and the remote vinyl carbons in the case of 4h and 4i (J(CSn) = 26 Hz, J(CPb) = 16 Hz) give experimental evidence for the intramolecular interaction and the charge transfer between the positively charged element and the remote C=C double bond. The experimental results are supported by quantum mechanical calculations of structures, energies, and magnetic properties for the norbornyl cations 4a,b (E = Ge, R = Me), 4c (E = Sn, R = Me), 4d (E = Pb, R = Me), and 4e,f at the GIAO/B3LYP/6-311G(3d,p)//MP2/6-311G(d,p) (Si, Ge, C, H), SDD (Sn, Pb) level of theory. The calculated (29)Si NMR chemical shifts for the silanorbornyl cations 4a,e,f (delta((29)Si) = 77-93) agree well with experiment, and the calculated structures of the cations 4a-f reveal their bridged norbornyl cation nature and suggest also for the experimentally observed species 4a,e-i a formally 3 + 1 coordination for the element atom with the extra coordination provided by the C=C double bond. This places five carbon atoms in the close vicinity of the positively charged element atom. The group 14 element norbornyl cations 4a,e-i exhibit only negligible interactions with the aromatic solvent, and they are, depending on the nature of the element group, stable at room temperature in aromatic solvents for periods ranging from a few hours to days. In acetonitrile solution, the intramolecular interaction in the norbornyl cations 4a,e-h breaks down and nitrilium ions with the element in a tetrahedral environment are formed. In contrast, reaction of acetonitrile with the plumbyl cation 4i forms an acetonitrile complex, 10i, in which the norbornyl cation structure is preserved. The X-ray structure of 10i reveals a trigonal bipyramidal environment for the lead atom with the C=C double bond of the cyclopentenemethyl ligand and the nitrogen atom of the acetonitrile molecule in apical positions. Density functional calculations at the B3LYP/6-311G(2d,p)//(B3LYP/6-31G(d) (C, H), SDD (Si, Ge, Sn, Pb)) + DeltaZPVE level indicate that the thermodynamic stability of the group 14 norbornyl cations increases from Si to Pb. This results in a relative stabilization for the plumbanorbornyl cation 4d compared to tert-butyl cation of 52.7 kcal mol(-)(1). In contrast, the intramolecular stabilization energy E(A) of the norbornyl cations 4a-d decreases, suggesting reduced interaction between the C=C double bond and the electron-deficient element center in the plumbacation compared to the silacations. This points to a reduced electrophilicity of the plumbacation compared to its predecessors.

A metal-free catalytic intramolecular hydrosilylation reaction is reported. The key intermediates in the catalytic cycle are silyl cationic species. The reaction is used to produce 2-silanorbornanes 2 from 3-cyclopentenemethylsilanes 1 under mild conditions and in high isolated yields.Key words: hydrosilylation, catalysis, silaheterocycles, silyl cations.

The title compound, C8H8O3, (I), crystallizes with two nearly identical molecules in the asymmetric unit. Each molecule has a boat conformation and noncrystallographic mirror symmetry. The structure was determined in connection with a study of the possible chemical decomposition of the compound in different solvents and in contact with the atmosphere. A similar boat conformation was found in five of six structures retrieved from the Cambridge Structural Database which contain (I) as a moiety. The present structure exhibits nearly the same packing motif as the recently found monoclinic polymorph.

2-Methoxynaphthalene, C11H10O, crystallizes as a nearly planar molecule, with the methoxy group adopting a synperiplanar conformation with respect to the C alpha atom. A search of the Cambridge Structural Database [Allen & Kennard (1993). Chem. Des. Autom. News. 8, 31-37] reveals that this conformation is characteristic of the alpha-methoxynaphthalene moiety, because, for each of the four exceptions found, a valid explanation can be given as to why they display a different conformation.