A quick method to determine the capacitance characteristics of thin layer X5R multilayer capacitors

The effect of Y2O3 concentration on the dielectric properties of ceramic disc capacitors and multilayer capacitors containing 50 dielectric layers with an approximate thickness of 3 μm were investigated. The relative permittivity and temperature coefficient of capacity of multilayer capacitors at low and high applied field suggest that two types of microstructures formed, depending on yttrium doping concentration. Yttrium concentrations of 1.5–2.0 mol% yielded identical relative permittivities over a wide temperature range. The permittivities at Y concentrations of 2.6–3.0 mol% were also identical, but somewhat higher. The relative permittivity of ceramic disc capacitors of similar composition, determined from hysteresis loop measurements as function of applied field, was compared with field-dependent permittivity measurements on multilayer capacitors. The results indicate that polarization measurements on CDCs are a good indicator for the relative permittivity values of MLCC

Fusing Cyclopentadiene and Ferrocene by Two Silyl Bridges Stereochemically Well-Defined Building Blocks for High-Nuclear Metallocenes.

The tetrahydro-4,4,8,8-tetramethyl-4,8-disila-s-indacenyl anion (LH) reacts with or without cyclopentadienyl anion (Cp−) and Fe2Cl4(THF)3 to give the mixed ferrocenes CpFe(LH) and (LH)2Fe in 50 and 63% yield, respectively. Near room temperature and in solution CpFe(LH) exists as a pair of enantiomers (syn-3a/b). According to an X-ray analysis both enantiomers are present in a single crystal. Compound 3 consists of a ferrocene linked to a cyclopentadiene by two Me2Si groups such that the acidic Cp proton points towards the iron. Temperature-dependent NMR spectra show that syn-3a and syn-3b are non-rigid molecules which are interconverted by 1,2-silatropic bond shifts (Ea = 49.2 ± 2.9 kJmol-1). Three more isomers (anti-3a, anti-3b, and the spiro derivative 3c), though present only in low concentration, are engaged in the rearrangement. (LH)2Fe is also non-rigid and exists as a pair of diastereomers (4a and 4b). The isomers of 3 and 4 undergo hydrolysis (e.g., syn-3a/3b gives [(Me2SiOSiMe2)Cp]FeCp (5) among others) and deprotonation. The latter yields CpFe(L–) (7) and (L−)2Fe (8), which are characterized by NMR spectroscopy. 7 forms crystals with [Li(TMEDA)]+ as counterion, and an X-ray analysis shows that lithium and iron are located at opposite sides of the strongly folded ligand L. The reaction of 7 with CrCl2(THF) gives the trinuclear stacked metallocene 9 in 47% yield. 9 has two unpaired electrons which are located essentially in the center of the molecule

The Elusive Structures of Pentakis [(triphenilphosphine)gold]ammonium(2+)Bis[tetraflouroborate(1-)]

{Pentakis[(triphenylphosphine)gold(I)]ammonium(2+)} bis[(tetrafluoroborate)(1-)] was prepared from {tetrakis-[(triphenylphosphine)gold(I)]-ammonium(1+)} [tetrafluoroborate(1-)] and [(triphenylphosphine)gold(I)] tetrafluoroborate in hexamethyl phosphoric triamide and tetrahydrofuran at 20 °C in 53% yield and crystallized from dichloromethane as the new solvate {[(Ph 3P)Au] 5N} 3 [BF 4] 6 [CH 2Cl 2] 4. The crystal structure of this product has been determined by single-crystal X-ray methods [monoclinic, P2 1/n, a = 34.200(3), b = 15.285(1), c = 53.127(3) Å, = 107.262(2)°, V = 26521(3) Å 3, Z = 12, at 153 K]. The lattice contains three independent trinuclear dications that have no crystallographically imposed symmetry and are mutually similar in their molecular structure. The geometry of the [Au 5N] core with pentacoordinate nitrogen atoms is intermediate between trigonal-bipyramidal and square pyramidal with severe distortions to minimize the Au-Au distances along some of the edges of the polyhedra. The three structures are thus different from that found previously in the tetrahydrofuran solvate {[(Ph 3P)-Au] 5N}(BF 4) 2(C 4H 8O) 2, where the geometry of the same trinuclear dication is closer to the trigonal-bipyramidal reference model. The new results are discussed in the light of the structures of tetra(gold)ammonium cations in salts of the type {[(Ph 3P)Au] 4N} +X - and of related tetra-, penta-, and hexacoordinate poly(gold)phosphonium, -arsonium, -sulfonium, and -selenonium cations