Metallic Square Research Articles

Reactivity of Diphenylacetylene with a Basal Edge-Bridged Square-Pyramidal Hexaruthenium Cluster. Characterization of Penta-, Hexa-, and Heptanuclear Alkyne Derivatives

The reactions of the basal edge-bridged square-pyramidal hexanuclear cluster [Ru6(μ3-H)2(μ5-η2-ampy)(μ-CO)2(CO)14] (1; H2ampy = 2-amino-6-methylpyridine) with 2 equiv of diphenylacetylene in toluene give 1 equiv of cis-stilbene and mixtures of cluster compounds, the composition of which depends on the reaction time and temperature. The following cluster compounds have been isolated and characterized: [Ru6(μ5-η2-ampy)(μ3-CO)(μ-CO)2(CO)14] (2), [Ru6(μ5-η2-ampy)(μ4-η2-PhCCPh)(CO)16] (3), [Ru7(μ5-η2-ampy)(μ5-η4-PhCCPh)(CO)17] (4), [Ru6(μ5-η2-ampy)(μ5-η8-PhCCPh)(μ-CO)(CO)13] (5), [Ru5(μ5-η2-ampy)(μ4-η2-PhCCPh)(μ-CO)(CO)12] (6), and [Ru5(μ5-η2-ampy)(μ4-η2-PhCCPh)(η6-PhMe)(μ-CO)(CO)9] (7). In all products, the nitrogen atoms of the ampy ligand are attached to five metal atoms, in the same way as in complex 1. While complex 2 has no alkyne ligand and can be considered as the result of a formal substitution of a CO ligand for the two hydrides of complex 1, the remaining products have a diphenylacetylene ligand capping the four atoms of a metallic square through both C atoms of the original triple bond. Additionally, an alkyne phenyl group of 4 is η2-coordinated to a ruthenium atom, while an alkyne phenyl group of 5 is η6-coordinated to a ruthenium atom. A reaction pathway that interconnects all these compounds is proposed. This has been deduced from the results obtained by following (by 1H NMR) the reaction of 1 with diphenylacetylene at different reaction times and temperatures (toluene, 80 and 110 °C), the reaction of 2 with diphenylacetylene (toluene, 110 °C), and the thermolysis of compounds 3−6 (toluene, 110 °C).

Triruthenium, Hexaruthenium, and Triosmium Carbonyl Derivatives of 2-Amino-6-phenylpyridine

The triruthenium cluster complexes [Ru3(I-H)(I3- 2 -HapyPh-N,N)(CO)9 ]( 1) and [Ru3(I‚)2(I3- 3 -HapyC6H4-N,N,C)2(CO)6 ]( 2) and the hexaruthenium ones [Ru6(I3-H)2(I5- 2 -apyPhN,N)(I-CO)2(CO)14 ]( 3) and [Ru6(I3-H)(I5- 3 -apyC6H4-N,N,C)(I-CO)3(CO)13 ]( 4) have been prepared from [Ru3(CO)12] and 2-amino-6-phenylpyridine (H2apyPh). Compound 1 contains a deprotonated HapyPh ligand capping a face of the metal triangle. Compound 2 contains two cyclometalated HapyC6H4 ligands, each spanning a Ru-Ru edge through the N atom of the amido fragment and chelating the remaining Ru atom through both the pyridine N atom and the C atom of the cyclometalated ring. The hexanuclear derivatives 3 and 4 have an uncommon basal edge-bridged square pyramidal metallic skeleton. The bridging ligand of 3 is a doubly deprotonated apyPh ligand which caps the metallic square through the exocyclic N atom, while is attached to the Ru atom that bridges the edge of the square pyramid through the pyridine N atom. Complex 4 is structurally related to 3 but has a cyclometalated phenyl ring. It has been established that compound 2 is formed by reaction of 1 with H2apyPh and that complex 3 is formed by reaction of 1 with [Ru3(CO)12]. While the hydrogenation of 4 gives 3, the thermolysis of 3 gives 4 among other unidentified products. The reaction of the osmium cluster [Os3(CO)10(MeCN)2] with H2apyPh gives a 1:5 mixture of the edge-bridged decacarbonyl derivatives [Os3(I-‚)(I- 1 -HapyPh-N)(CO)10 ]( 5) and [Os3(I-H)(I- 2 -HapyPhN,N)(CO)10 ]( 6). Both compounds give the face-capped nonacarbonyl derivative [Os3(I-H)(I3- 2 -HapyPh-N,N)(CO)9 ]( 7) upon irradiation with UV light. Curiously, while complexes 5 and 7 are stable in refluxing toluene, the thermolysis of 6 gives a mixture of 5, 7, and the cyclometalated dihydride [Os3(I-H)2(I- 3 -HapyC6H4-N,N,C)(CO)9 ]( 8).

Shielding effect using cascaded metallic holes in microwave circuits

The problem of electromagnetic shielding between elements of microelectronic circuits has been studied by using a new technique (the via holes technique). Metallic squares and truncated square cross sections approximate each metallic circle cross section. A comparison between the adjacent and a staggered arrangement of via holes has been illustrated theoretically and experimentally. © 2001 John Wiley & Sons, Inc. Microwave Opt Technol Lett 29: 322–324, 2001.

Microstrip antenna coupling for quantum-well infrared photodetectors

We computed the expected performance of microstrip antennas as optical couplers in quantum-well infrared photodetectors (QWIPs) by the finite-difference time-domain technique. The microstrip antenna consisted of a metal square that is placed on one side of a thin QW stack, across from a continuous ground plane on the other side of the stack. The size of the square was one-half wavelength in the QW material, or ∼1.2 μm for a long-wavelength GaAs/AlGaAs QWIP. An array of these antennas can be used to couple to an arbitrary-size pixel. Unlike the elements of a diffraction grating, each antenna in the array acts as a nearly independent coupler whose peak wavelength is determined by the dimensions of the antenna, not by the period of the antenna array. Because of this local coupling, the array of microstrip antennas maintains absorption in small pixels much more effectively than do grating couplers. Furthermore, the microstrip antenna yields moderately high absorption over a useful spectral bandwidth with a very thin QW stack. Such a stack has a high photoconductive gain, which is useful for many applications.

Shielding effect using cascaded metallic holes in microwave circuits

AbstractThe problem of electromagnetic shielding between elements of microelectronic circuits has been studied by using a new technique (the via holes technique). Metallic squares and truncated square cross sections approximate each metallic circle cross section. A comparison between the adjacent and a staggered arrangement of via holes has been illustrated theoretically and experimentally. © 2001 John Wiley & Sons, Inc. Microwave Opt Technol Lett 29: 322–324, 2001.

Finite element simulation of the axial collapse of thin-wall square frusta

In vehicle crashworthiness studies special effort has been spent on experimental research and in establishing safe theoretical design criteria on the mechanics of crumpling, providing, in this manner, to the engineers the ability to design safe vehicle structures, so that the maximum amount of the crash energy will dissipate while the material surrounding the passengers department is deformed. Generally, this energy absorbing capability depends upon the governing deformation phenomena of all or part of structural components of simple geometry, such as thin-walled tubes, cones, frames, sections etc. In particular, the crash analysis of plated structural components has been traditionally based on destructive prototype testing and requires analytical and/or numerical theoretical models to incorporate in detail the main crash phenomena, i.e. local buckling, post-buckling and maximum strength of each section and the various crumpling mechanisms expected. For this purpose, specialized finite element codes have been developed to establish efficient design of energy absorbing systems. The main objective of the present paper is to apply the explicit FE code LS-DYNA to the simulation of the crash behaviour of metallic thin-walled square frusta subjected to axial compression. The results taken from the simulation, in comparison to the actual experimental data on similar specimens, agree on many aspects and the concluding remarks pertaining to the design of the crushing process are drawn.

Hydroxynaphthoquinone Metal Complexes as Antitumor Agents X: Synthesis, Structure, Spectroscopy and In Vitro Antitumor Activity of 3‐Methyl‐Phenylazo Lawsone Derivatives and Their Metal Complexes Against Human Breast Cancer Cell Line MCF‐7

The C-3 substituted phenylazo derivatives of lawsone (2-hydroxy-l,4 p-naphthoquinone, III) were synthesized and characterized. The X-ray crystal structure was determined for the ligand 3-(3′-methyl phenylazo) lawsone. The copper complexes of these derivatives were found to possess 1:2 metal stoichiometry and square planar geometries with intermolecular stackings, resulting in antiferromagnetic exchange interactions. The in vitro activity of all the synthesized compounds was examined against human breast cancer cell-line, MCF-7, which revealed enhanced activities for the metal complexes, the highest activity being observed for the copper compound of 3-(3′-methyl phenylazo) lawsone.

Acetylene incorporation into the spiked framework of the phosphinidene and arsinidene clusters [Ru4(CO)13(μ-H)2(μ4-ECF3)] (E = P or As): skeletal rearrangement and crystal structures of a series of tetranuclear ruthenium clusters bearing alkynes

Reactions of [Ru4(CO)13(µ-H)2(µ4-ECF3)] (E = P 1 or As 2) with RCCR (R = Ph or H) under mild conditions yielded square planar clusters [Ru4(CO)9(µ-CO)2(µ4-ECF3)(RC2R)] (E = As, R = Ph 3; E = P, R = Ph 4 or E = P, R = H 5) in which the acetylene ligands are attached to the metal square planes via 2σ + 4π bonds. Under similar conditions, the reaction of 1 with CF3CCCF3 afforded a similar cluster [Ru4(CO)12(µ4-PCF3)(CF3C2CF3)] 6 in which the acetylene interacts with the Ru4 square face only by 4σ bonds. Reactions of 1 and 2 with MeCCMe resulted in metal skeletal rearrangement and P–C bond formation to form the butterfly cluster [Ru4(CO)10(µ-CO)2{CF3PC(Me)C(Me)}] 7 and alkyne dimerization at the spiked Ru atom to form spiked clusters [Ru4(CO)9(µ-CO)2(µ4-ECF3)(C4Me4)] (E = P 8 or As 9) containing a metallocyclic RuC4Me4 ring. Reaction of 1 with diphenylbutadiyne under similar conditions afforded a square planar cluster [Ru4(CO)11(µ4-PCF3){PhC(H)C(H)CCPh}] 10 where the bridging hydrogen migrates to the diyne to form a 1,4-diphenylbut-3-en-1-yne fragment attached to the Ru4 face.

The synthesis and characterization of Ni, Pd and Pt maleonitriledithiolate complexes: X-ray crystal structures of the isomorphous Ni, Pd and Pt (Ph2PCH2CH2PPh2)M(maleonitriledithiolate) congeners

The synthesis of a series of maleonitriledithiolate complexes of nickel, palladium and platinum phosphines having the formulae (dppe)M(mnt) and (Ph3P)2M(mnt) (where dppe = Ph2PCH2CH2PPh2, mnt = 1,2-dicyanoethene-1,2-dithiolate and M = Ni, Pd or Pt) from the reaction of Na2(mnt) and the appropriate (phosphine) MCl2 is reported. These complexes were characterized by a combination of mass spectrometry, IR, UV-Visible and 1H. 13C and 31P NMR spectroscopy. In addition, characterization of the title complexes by single crystal X-ray diffraction of all three congeners revealed them to be isomorphous. Analysis of the diffraction data reveals that the metal centers are all square planar, that the planar mnt ligands are tilted slightly away fro the metal square planes, and that the mnt ligand is best described as a dithiolate rather than a dithione.

Five-coordinate hydrogen in hydrido rhodium cluster compounds: A theoretical analysis

The electronic structure of the hydrido species [H 2Rh 13(CO) 24] 3− containing H atoms inserted in square pyramidal holes is analyzed using DFT calculations. In particular, the covalent nature of the hydrogen-metal bonding is demonstrated, due to an effective interaction of the H orbitals with high-lying FMOs of the centered anti-cuboctahedral Rh 13 core. The position of the hydrogen atoms in the square pyramidal cavities is mainly governed by the arrangement of the carbonyl ligands tethered to the metallic square faces. In agreement with the structural data, DFT computations favors the isomer with the H atoms encapsulated in the cavities having the smallest number of bridging CO ligands.

Rutheniuminduzierter abbau von tetramethylthioharnstoff zu carbenliganden. Synthese und molekülstruktur der cluster Ru 4(μ2-CO)2(CO) 9-n(μ 4-S) 2[C(NMe 2) 2] n (n = 1, 2) und (μ 2-H)Ru 3(CO) 9[μ 3-SRu 3(CO) 3(η 2-CH 2 NMeCNMe 2)

Tetramethylthiourea was found to react with Ru 3(CO) 12 in refluxing THF to give sulphur- and diaminocarbene-containing clusters. The X-ray diffraction studies of the resulting clusters Ru 4(μ 2-CO) 2(CO) 9- n ,(μ 4-S) 2[C(Nme 2) 2] n . ( n = 2: 5; n = 1: 6) show square-planar metal frameworks, capped on both sides by μ 4-sulphido ligands. The diaminocarbene ligands in 5 are coordinated in a transoid fashion to two opposite ruthenium atoms of the metal square; cluster 6 can formally be derived from 5 by replacement of a diaminocarbene ligand by a carbonyl ligand. The X-ray analysis of a further product, the cluster (μ2-H)Ru 3(CO) 9[μ 3-SRu(CO) 3(η 2CH 2NMeCNMe 2)] ( 7), shows a ruthenium triangle capped by a μ 3-sulphido ligand. A fourth ruthenium atom, coordinated to sulphur, carries a η 2-trimethylmethylenediaminocarbene ligand; the formation of this unusual four-membered metallacy cle is caused by CS and, CH activation of the tetramethylthiourea. Another reaction product is the light-sensitive complex (μ 2-H)Ru 3(CO) 8(μ 3-S) (η 2-CH 2NMeCNMe 2) ( 8) which contains a three-membered metal triangle, capped by a μ 3-sulphido ligand; as in 7, a η 2-trimethylmethylenediaminocarbene ligand is coordinated to one of the ruthenium atoms. An isomer of 8, the cluster (μ 2-H)Ru 3(CO) 8(μ 3-S) (μ 2-η 2-CH 2NMeCNMe 2) ( 9), in which the η 2- trimethylmethylenediaminocarbene ligand bridges an edge of the ruthenium triangle, is also isolated from the reaction mixture.

Percolational and fractal property of random sequential packing patterns in square cellular structures.

The problem for random packing or filling has been treated in many fields. In this paper we form random sequential packing patterns, filling metallic squares with integer length a on insulator substrates divided into square unit cells. We investigate the percolational and fractal property of the packing patterns, and clarify that the maximum critical percolation length ${a}_{c}$ (=3 units length) of the packed squares is presented for the insulator-to-metal transition to take place on the random sequential packing textures. When a>${a}_{c}$, no insulator-to-metal transition occurs even at the saturation coverage where no more squares can be filled without any overlap. However even in such patterns with a>${a}_{c}$, the large percolation clusters possess fractal properties, and the fractal dimensions equal 1.94.

Cyclopropenylidenetransition metal complexes: synthesis and structure of cis-dichloro(tri-n-butylphosphine)(bis( N,N-dimethylamino)cyclopropenylidene)-palladium(II)

The synthesis of cis-dichloro(tri-n-butylphosphine)(bis( N,N-dimethylamino)-cyclopropenylidene)palladium(II), cis-PdCl 2[C(Me 2NC) 2](P-n-Bu 3), from the reaction of [PdCl 2(C(Me 2NC) 2)] 2 with P-n-Bu 3 is described. The first precise analysis of the structure of a cyclopropenylidene—transition metal complex has been carried out. The C 3-ring is bound through the unique carbon atom to the metal center with a PdC distance of 1.961(3)Å and is roughly perpendicular to the metal square plane. All CC ring distances are equivalent within experimental error and average 1.383(2)Å. The dimethylamino groups are sp 2 hybridized at the nitrogen atoms and are coplanar with the carbbocyclic fragment. The compound crystallizes in the monoclinic space group C 5 2 h - P2 1/ c with four molecules in a cell of dimensions a 7.933(4), b 15.524(6), c 19.572(7)Å, β 101.05(2)°, V 2326Å 3 ( T-160°C). The final values of R and R w for the 226 variables and 4383 significant observations are 0.036 and 0.042. Characteristic spectroscopic (IR and NMR) data for the compound are reported.

Operation of metal-halide lamps on square wave supply

In a comparison of the operation of high pressure metal halide lamps, on either sine or square wave supplies lamps have been found to operate satisfactorily using both choke and choke/capacitor ballasts. The dependence of lamp power on supply waveform and ballast type has been measured on 250 W MBI lamps for a supply voltage range of 210-270 V. Analysis of the lamp circuit for square wave supply voltage has been made using the simplifying assumption that the lamp voltage is independent of current. Expressions derived for the current waveforms and the power dissipated in the lamp are shown to agree well with experimental values. Although the analysis is used to predict the behaviour of metal-halide lamps, it is equally valid for other types of discharge lamps.

FACTORS IN THE ECOSYSTEM OF FOOD PROCESSING EQUIPMENT CONTRIBUTING TO OUTGROWTH OF MICROORGANISMS ON STAINLESS STEEL SURFACES

A laboratory system using 1 cm2 pieces of stainless steel with controlled temperature, humidity, and inocula was used to study the fate of the microflora of dairy origin on various films. Metal squares were treated to simulate incomplete cleaning, then inoculated with raw milk. After incubation for 16 hr at 80, 86, 93, or 100% RH, the microflora was recovered in sterile phosphate buffer and evaluated using the standard plate count method. Isolates from countable plates were observed for general characterization.Humidity of the ecosystem was a major factor in rate of water loss from a film. Available water, and indirectly the solute concentration, influenced the microenvironment and the resulting population density of microorganisms. Likewise, the microenvironment had a selective effect on outgrowth of bacteria, because of varying sensitivity of bacteria to drying and solute concentration. The gram-negative bacteria were inhibited at a lower humidity (80% RH), while the higher humidities (93 or 100% RH) provided sufficient water for abundant outgrowth. Reduction of area of a film exposed to air reduced water loss and provided protection for harborage of microorganisms.Pre-soiling prior to addition of a film of milk decreased the rate of water loss from the film and increased bacterial growth. Induced lipolysis within a film of milk influenced outgrowth of bacteria with an inhibitory effect on gram-positive types. Results indicate that modem closed systems and extensive mechanical handling of milk may be favoring growth of undesirable gram-negative bacteria, e.g., coliforms and psychrotrophs.