A-frame Structure Research Articles

Performance Assessment of Japanese Mint Varieties for Growth under Open Field and Vertical A-Frame Structure

Japanese mint (Mentha arvensis L.), is a member of the family Lamiaceae which is a perennial herbaceous aromatic plant but cultivated as an annual for culinary purpose as leafy vegetable and as natural menthol extraction. It is a major source of raw material for flavours and fragrance industry. Urban regions are losing cultivable land every day and it has become extremely difficult to produce fresh vegetables of high quality. By using vertical structures, vertical space can be utilized while increasing the quality of vegetable production. This experiment was conducted at Department of Vegetable Science, Horticultural College & Research Institute, Periyakulam during 2022-2023 to evaluate the performance of nine varieties viz., Kosi (V1), CIM-Kranti (V2), Himalaya (V3), Kalka (V4), MAS-1 (V5), Saksham (V6), Gomti (V7), Seelayampatti local (V8) and Bangalore hybrid (V9) under open field (G1) and vertical A-frame structure (G2) condition. One vertical A-frame structure is used in this study which contain 516 holes for planting. Among the nine varieties, Saksham (V6) showed increase in growth parameters in both conditions. The observations on growth parameters were recorded for plant height(cm), number of leaves, root length(cm), fresh weight of roots(g) and dry weight of roots(g). Saksham variety in vertical A-frame structure yielded maximum plant height (53.05 cm), number of leaves (112.73), root length (39.92 cm), fresh weight of roots (3.204g) and dry weight of roots (0.874g) followed by the variety CIM-Kranti in vertical A-frame structure (48.83cm, 77.61, 37.75cm, 2.582g and 0.648g). As a result, the interactive action of G2V6 showed maximum growth due to the availability of nutrients in the root system and timely application of water and nutrient helped in better plant parameters.

Experimental Testing on an Air-Cooled Condenser Motor, Gearbox and Fan

The majority of South Africa’s electricity is generated from coal-fired power stations. After expansion through the turbine stage the heated steam is condensed by air-cooled condensors (ACCs). In water scarce areas air-cooled condensers are used to reject heat by means of convection through an array of fans that force air over the heated steam tubes positioned in a A-frame structure above the fan. The ACC system consists of an induction motor, two-stage gear reducer and an axial fan. For this research, the rotational velocity of the gearbox’s output shaft is measured as well as the bending and torsional strain experienced during different stages of operation. A proximity sensor and various sets of strain gauges are used to record the measurements respectively. Testing was conducted at three different sites that utilize different control methods for the induction motors. The purpose of testing at different sites was to evaluate the effectiveness of each start-up control system and its application inside an ACC. The results obtained in each of the three cases are quite clear that any motor controller is beneficial to the overall system simply due to the reduced inrush current and torque peaks.

Thermal analysis of oil sump and compression unit in a rotary compressor

Thermal analysis of the oil sump and compression unit in a hermetic rotary compressor is important for enhancing its performance and reliability. In this study, the temperature distribution, heat-transfer mechanism, and heat balance of the oil sump and compression unit in a rotary compressor were analyzed using the 3D computational fluid dynamics (CFD) fluid-solid coupled model. Considering the practical characteristics of the rotary compressor, some special treatments are proposed for the simulation model. Instead of using empirical formulations, heat-transfer coefficients in the upside of the main bearing and compressor shell were obtained using the 3D CFD simulation model; the dynamic process in the suction chamber and compression chamber was considered to be static and the oil film in the inner wall of the cylinder, rib effect of the A-frame structure at the bottom of the compressor shell, and friction loss in the side of the sliding vane were considered. The simulation results showed good agreement with experimental results. We expect that these analytical results would be of great use in further understanding the temperature distribution and heat-transfer mechanism of oil sumps and compression units and also provide guidelines for improving the performance and reliability of rotary compressors.

Damage Detection in Frame Structure Using Piezoelectric Actuator

Health-monitoring and On-line damage detection techniques on frame structures are stronglyneeded.Vibration based methods with piezoelectric sensor and actuator integrated into structures is a promising option to fulfil such requirements. This paper presents use of piezoelectric actuator to detect bolt loosening in a frame structure. Frequency response function (FRF) method is used along with piezoelectric actuator. These methods utilize finite element analysis techniques, together with to detect damage. They locate and estimate damage by comparing dynamic responses between damaged and undamaged structures. AFrame structure is modelled using finite element software ABAQUS. Frame structure is coupled with piezoelectric actuator which excites the structure for transient analysis. Acceleration responses are measured at various points in structure and this data is used to find out frequency response functions (FRF). The shift in the natural frequencies of the structure is observed for undamaged and damaged structure to detect the damage.

Evaluación de sustratos en un cultivo de lechuga bajo un sistema hidropónico en el municipio de Pasto

La horticultura es un importante renglón económico en Nariño, este proyecto se realizó como una alternativa para mejorar la producción y calidad de lechuga. En el Centro Internacional de Producción Limpia Lope - SENA - Regional Nariño, se realizó la evaluación de los sustratos fibra de coco y cascarilla de arroz con sus respectivas mezclas bajo un sistema hidropónico sobre una estructura en forma de “A” para la producción de lechuga (Lactuca sativa L.) en un área de 10 metros2 para un total de 200 plantas, donde se evaluaron las variables altura, diámetro, peso total, peso de cabeza, peso de raíz y rendimiento. Se utilizó un diseño irrestrictamente al azar, con 5 tratamientos y 4 repeticiones, con los siguientes tratamientos; sustrato 100% cascarilla de arroz, mezcla de 70% cascarilla de arroz y 30% fibra de coco, mezcla del 50% de cada uno de los sustratos utilizados, mezcla 70% fibra de coco y 30% cascarilla de arroz y el tratamiento de sustrato 100% fibra de coco. Las mezclas de los sustratos fibra de coco y cascarilla de arroz obtuvieron mejor respuesta para las variables evaluadas que los sustratos individuales, los cuales dieron plantas con mejor desarrollo fisiológico en las variables diámetro peso de cabeza, y rendimiento. En cuanto a la rentabilidad el tratamiento 70% fibra de coco y 30% cascarilla de arroz fue el mejor con un porcentaje del 12%.

Evaluation of Enhanced Heat Transfer Within a Four Row Finned Tube Array of an Air Cooled Steam Condenser

Air cooled steam condensers (ACSC) consist of finned-tube arrays bundled in an A-frame structure. Inefficient performance under extreme temperature operating conditions is a common problem in ACSCs. The purpose of this study was to improve the heat transfer characteristics of an annular finned-tube system for better performance in extreme climatic conditions. Perforations were created on the surface of the annular fins to increase heat transfer coefficient (h). Mesh generation and finite volume analyses were performed using Gambit 2.4.6 and Fluent 6.3 with an RNG k–ϵ turbulent model to calculate pressure drop (ΔP), heat flux (q), and heat transfer coefficient (h). Solid (no perforations) finned-tubes were simulated with free stream velocity ranging between 1 m/s–5 m/s and validated with the published data. Computations were performed for perforations at 30° interval starting at ±60°, ±90°, ±120°, ±150°, and ±180° from the stagnation point. Five cases with single perforation and three cases with multiple perforations were evaluated for determining the maximum q and h, as well as minimum ΔP. For the perforated case (perforations starting from 60° at interval of 30°), the fin q and h performance ratios increased by 5.96% and 7.07%, respectively. Consequently, the fin ΔP performance ratio increased by 11.87%. Thus, increased q and h is accompanied with a penalty of higher ΔP. In contrast, a single perforation location at 120° provided favorable results with a 1.70% and 2.23% increase in q and h performance ratios, respectively, while there was a relatively smaller increase (only 1.39%) of ΔP performance ratio. Perforations in the downstream region at ±120°, ±150°, and ±180° also resulted in a similar favorable outcome. Furthermore, the spacing of the fins along the arms of an A-frame ACSC was altered to decrease ΔP across the finned-tube array. Fin spacing in the A-frame structure with sparsely spaced fins in the center resulted in a 1.80% reduction in ΔP. Thus, penalty in ΔP for a perforated fin can possibly be offset by changing the fin spacing along the arms of an A-frame structure.

Ice (review)

Reviewed by: Ice Elizabeth Bush Geisert, Arthur. Ice; illus. by Arthur Geisert. Enchanted Lion, 2011. 28p. ISBN 978-1-59270-098-1 $14.95 R* Gr. 5–9 yrs. On an isolated, treeless island in the watery back of beyond, a community of pigs lives in tiny A-frame structures tented against the punishing sun. Their cistern is so low that a bucket brigade has to descend therein to haul water up to the houses. Everyone is drooping, and even the electric fan fails to bring relief. But if these pigs are staring Death in the face, they show no signs of worry. A calm, smiling committee of men, women, and children (okay—boars, sows, and piglets) consults a globe and springs into action. A ship that was apparently grounded on the edge of the island is called back into service as the elaborate gondola of an airship, and a plucky expedition is off to northern seas to procure an iceberg. Moored to the island, the berg is sawed up into blocks of ice, which are then hoisted into the cistern; a lively pool party ensues, and soon the residents are enjoying piped-in water, pitchers of iced drinks, and improvised air conditioning. Geisert’s signature wordless books have always been distinguished for the intricate kludges that power piggy technology, and Iceis no exception. Two epicenters of technical delight invite viewers to marvel at porcine inventiveness. First is the water supply system, rendered as a simple but effective array of conduit that connects the massive stone cistern with the individual houses, where convenient hand pumps are located right at each doorway. And then there’s the ship: provocatively high and dry at the book’s opening, the craft reveals its true nature as the adventurers ready her for the journey. The metal contraption on deck proves to be a boiler, which inflates massive red balloons with hot air, while square-rigged sails catch the wind aloft. The extra mast, yard, and furled sails that dangle below the keel on the outbound trip are ultimately attached to the iceberg; guided by a rudder that’s manned (pigged?) by a small crew, the iceberg is towed home. While one landing party disassembles the rigging, the awaiting islanders build the gangplanks and hoists to move ice from berg to cistern. The whole operation is accomplished with a “No problem, no worries” insouciance that turns menacing drought into a group lark, proving the old adage “Many hooves make light work.” Although these pigs demonstrate the wondrous resourcefulness that Geisert fans have come to expect, it’s their surreal setting that steals the show. This title is as much about big questions as small details, and the audience is compelled to ponder and create a backstory that can account for the community’s predicament and its quirky resolution. Did the pigs choose to settle on such a barren outpost, or was the island scoured bare by some natural or manmade disaster? Did they arrive by airship, or did they modify a seagoing vessel? (Geisert aficionados who go way back might even wonder whether this is the last vestige of a dismantled [End Page 405] Ark.) What do they eat? Does their airship make regular supply forays? How did they build their cistern? And how, for the love of Mike, do they power that electric fan? Each answered question helps the reader plot a unique Choose Your Own Adventure–style narrative, which can range from nerdy technological conjecture to ambitious myth-making. Although the exigencies of Bulletinheadings demand the application of an age/grade code, this is about as close to a true All Ages title as you can get. Etchings tinted in colors that recall antique maps (cartographical uncertainty acknowledged, perhaps, with a marginal speculation, “Here there be Piggies”?) boast an appeal that crosses generations, and the absence of text allows pre-, non-, and skilled readers to meet on common ground. Although the small trim size suggests solo reading or a small, tightly huddled group of viewers, even the dullest of Geisert’s pigs could figure out how to rig a document camera and projector to facilitate larger storytime sharing. This may be...

Probing the Electronic Communication of the Isocyanide Bridge Through the Luminescence Properties of the d9−d9 [ClPt(μ-dppm)2Pt(C≡N—PCP)]+ and A-Frame [ClPd(μ-dppm)2(μ-C═N—PCP)PdCl] Complexes

The homodinuclear d9-d9 ClM(mu-dppm)2MCl2 complexes, 1 (M ) Pt) and 2 (M ) Pd) react with the conjugated and luminescent PCP-NC ligand (3, PCP ) [2.2]paracyclophane) to provide the corresponding d9-d9 terminal[ClPt(mu-dppm)2Pt(CNsPCP)]Cl (4) and d8-d8 A-frame [ClPd(mu-dppm)2(mu-CdNsPCP)PdCl] (5) isocyanide complexes, respectively. These two bimetallic complexes were characterized by IR, 1H, and 31P{1H} NMR and bychemical analysis. IR data (nu(CN) bridging vs terminal) reveal a terminal isocyanide bonding mode for 4 (2147cm(-1)) and an A-frame structure for 5 (1616 cm(-1)). The optical and emission properties of the free isocyanide 3as well as those of the homodinuclear complexes 4 and 5 were studied by UV-visible and luminescence spectroscopy and by photophysical measurements. The unexpected presence of simultaneous intraligand pipi* fluorescence and phosphorescence attributable to the organic PCP-NC ligand, as well as luminescence from the inorganic M2-bonded Pt2(mu-dppm)2 center arising from a lower energy excited LMCT state (ligand-to-metal-charge-transfer) for4 at 77 K, indicates a weak conjugation between the two chromophores and an absence of efficient singlet andtriplet energy transfers. For 5, only the fluorescence and phosphorescence bands of the PCP-NC ligand are observed [since the A-frame XPd(mu-dppm)2(mu-L)PdX (L ) isocyanide, X ) halide) is not luminescent], stressing that the NtC bridge exhibits modest electronic communication properties.

The First A-Frame-Containing Organometallic Polymer: Taking Advantage of the Site Selectivity in PdPt-Mixed Metal Bimetallics

ClPd(l-dppm)2PtCl (1) reacts with (CNC6H4- 2-OCH2-)2 to form a sparingly soluble and thermally stable orange polymeric material 4. 1 reacts with 1 or 2 equiva- lents of CNC6H4-2-OCH3 to form the soluble A-frame d 8 - d 8 model complexes 2 (ClPd(l-dppm)2(l-CNR)PtCl), and 3 (ClPd(l-dppm)2(l-CNR)Pt(CNR))(Cl) (R = C6H4-2- OCH3), respectively. IR (m(NC) bridging versus terminal) and NMR data reveal an A-frame structure where the ter- minal CNR ligands are bonded to Pt. 4 which is amorphous (XRD) appears stable up to 290 C (TGA), but exhibits an exothermic process between 215 and 255 C upon the first scan in DSC, but disappears upon the second. Two com- pounds, model 2 (ke = 674 nm; se = 0.38 ± 0.01 ls; Ue = 0.0079 (±10%)) and polymer 4 (ke = 660 nm; se = 0.18 ± 0.01 ls; Ue = 0.0056 (±10%)) are luminescent at 77 K in the solid state and in fluid solution (PrCN).

Synthesis and structural analysis of palladium biscarbene complexes derived from bisimidazolium ligand precursors

The palladation of potentially chelating bisimidazolium ligand precursors with palladium acetate gives bridging bimetallic, chelating monometallic, and homoleptic tetracarbene complexes. The coordination mode of the biscarbene ligand has been identified by spectroscopic analysis and crystallographic characterization of representative complexes, including the first example of a biscarbene A-frame structure. Substantial concentrations of free acetate favor the formation of tetracarbene over biscarbene palladium complexes, while in the absence of a base, the concentration of reactants influences the selectivity for bridging bimetallic versus chelating monometallic species. Preliminary kinetic and mechanistic studies indicate that chelating biscarbene palladium acetate complexes are intermediates in the formation of the homoleptic tetracarbene complexes. Probably due to the high trans effect of the biscarbene ligand, such complexes are more efficient palladating agents for bisimidazolium salts than palladium acetate.

Canada remembers

Canada remembers

Electrochemical reduction properties of A-frame compounds and crystal structure of Pd 2(dppm) 2(Me) 2(Br) + dimer

Two series of A-frame complexes, [Pd 2(dppm) 2(R) 2(μ-X)] + (R = Me and X = Cl, Br, I, H; R = Mes and X = Br, I), were investigated by cyclic voltammetry (CV). The 2-electron reduction potentials for the first series increase from I (−1.10), Br (−1.17), Cl (−1.25) to H (−1.65 V versus SCE, in CHCl 3), as well as in the second series; Br (−1.35) and I (−1.38 V versus SCE, in THF). The nature of the LUMO where the electron reduction takes place is qualitatively addressed by DFT on the corresponding model complexes [Pd 2(H 2PCH 2PH 2) 2(R) 2(μ-X)] +. The LUMO and (LUMO + 1) of the halide derivatives exhibit the presence of Pd d x 2 - y 2 atomic orbitals interacting in an anti-bonding fashion with the n-donor orbitals of X −, P, and Me −, explaining in part the observed reactivity upon reduction. The X-ray structure of [Pd 2(dppm) 2(Me) 2(μ-Br)] + compound exhibits the typical A-frame structure with a Pd⋯Pd non-bonding distance of 3.036(1) Å, and long Pd–Br bonds of 2.5623(5) and 2.5793(5) Å.

Enlarging the family of ferrocenylphosphine dinuclear rhodium complexes: synthesis and X-ray structure of a novel “A-frame”-type trimetallic Rh/Fe/Rh complex

The symmetrically substituted ligand 1,1 ′-bis[di(5-methyl-2-furyl)phosphino]ferrocene ( 1) has been obtained from the bromophosphine BrP(Fu Me) 2 and the dilithioferrocene/TMEDA adduct. The quantitative addition of this ferrocene derivative to the tetracarbonyl dimer [(CO) 4Rh 2{μ-(S t Bu) 2}] leads, through decarbonylation, to the dinuclear rhodium complex [(CO) 2Rh 2{μ-(S t Bu) 2}{μ- P, P-Fc[P(Fu Me) 2] 2}] ( 2) in high yield. A X-ray structure [ orthorhombic, space group P2 12 12 1; a=11.2982(2) Å, b=13.3165(3) Å, c=27.2687(7) Å] and the solution multinuclear NMR characterization are reported, which show that the rare “quasi-closed bridging” A-frame structure of the complex is rather similar to the one reported for [(CO) 2Rh 2{μ-(S t Bu) 2}{μ- P, P-dppf}] in solid state. However, in solution the furyl-containing ferrocenylphosphine complex presents a greater fluxionality, together with an electronic environment at phosphorus very different from the dppf analogue ( δ P=−10 and 27 ppm, respectively).

Reactivity and electrochemical properties of the d 8–d 8 Pd 2(dppm) 2(Cl) 2(Me) 2 towards MeI

The title dimer reacts with MeI or KI to form [Pd 2(dppm) 2(μ-I)(Me) 2]I. The latter has been characterized from X-ray crystallography, and exhibits a A-frame structure with a Pd⋯Pd separation of 3.061 Å. The 4-electron reduction of the d 8–d 8 title starting material Pd 2(dppm) 2(Cl) 2(Me) 2 and resulting [Pd 2(dppm) 2(μ-I)(Me) 2]I product in the presence of dppm, produces the known Pd 2(dppm) 3 dimer. The presence of intermediates such as the d 9–d 9 ‘Pd 2(dppm) 2(Me) 2’ and d 10–d 10 ‘Pd 2(dppm)2(I) n n− ’ species are suspected, and 31P NMR indicates evidence for the relatively unstable mononuclear Pd(dppm)(Me) 2 complex. The reductive electrolysis of both d 8–d 8 dimers in the presence of an excess of MeI leads to an increase in Pd(dppm)(Me) 2 concentration.

Synthesis and Structures of Palladium and Platinum A-Frame Complexes Bridged by a Novel Binucleating Ligand,N,N‘-Bis[(2-diphenylphosphino)phenyl]- formamidine

A novel binucleating ligand, N,N‘-bis[(2-diphenylphosphino)phenyl]formamidine (Hdpfam), has been prepared and utilized for the synthesis of homo- and heterobimetallic palladium/platinum complexes M2R2(μ-X)(μ-dpfam) (M = Pd, Pt; R = Me, p-Tol, Cl; X = Cl, Br, I; dpfam = N,N‘-bis[(2-diphenylphosphino)phenyl]formamidinate). Treatment of Hdpfam with 2 equiv of MRX(tmeda) or MRX(cod) in the presence of tmeda produced the homobimetallic complexes. The heterobimetallic complex PdPtMe2(μ-Cl)(μ-dpfam) was obtained by the reaction of PdMeCl(cod) with PtMe(dpfam), which was produced from PtMe2(cod) and Hdpfam. The crystal structures of Pd2Cl2(μ-Cl)(μ-dpfam) and Pt2Me2(μ-Cl)(μ-dpfam) have been determined by X-ray analysis. The results indicate that both complexes have P−M−Cl−M−P A-frame structures, in which each metal center has a slightly distorted square-planar geometry and the nonbridging σ-donor ligands (Cl or Me) and μ-Cl are in a cis orientation. Treatment of Pt2Me2(μ-Cl)(μ-dpfam) with NaBH4 gave the hydride-br...

Chromium(II) complexes bearing 2-substituted N,N ′-diarylformamidinate ligands

A study regarding the interaction of several ortho ring-substituted N,N′-diarylformamidinate ligands (DPhXF, X = Me, OMe, Cl and Br) with the Cr24+ moiety has been undertaken. X-Ray diffraction and spectroscopic data have shown that while all of these ligands form the well-known paddlewheel type complex Cr2(DPhXF)4, 1 [X = Me, OMe, Cl and Br; Cr–Cr = 1.925(1), 2.140(2), 2.208(2) and 2.272(2) Å, respectively], two of them form highly unusual A-frame type complexes with short Cr–Cr bonds, and the smallest M–X–M angle ever reported in an A-frame structure. These are Cr2(μ-Cl)(DPhXF)3, 2 [X = Cl and Br; Cr–Cr = 1.940(1) and 1.940(2) Å, respectively]. For some of the paddlewheel complexes, the elongation of the metal–metal bond distance out of the ‘super-short’ range (Cr–Cr > 2.00 Å) has been attributed to the presence of axial interactions between two of the ortho substituents and the Cr24+ moiety.

An unusual cyanide-bridged extended A-frame complex: the molecular structure of [Pd 2Br 2(μ-PPh 2)(μ-dppm) 2(μ-CN) 2

The tetranuclear palladium complex [Pg 2Br 2(μ-PPh 2)(μ-dppm) 2(μ-CN) 2] was isolated by slow crystallization of an acetone solution, and its solid state structure has been determined by X-ray crystallography. The molecule is composed of two dppm-bridged dipalladium moieties held together by two cyano ligands. It adopts an extended or double A-frame structure, with the additional bridging PPh 2 groups occupying sites on opposite faces of the Pd 4 unit.

Hydride-bridged dipalladium complexes containing diphosphine ligands

A series of hydride-bridged dipalladium complexes supported by bis(diphenylphosphino) methane (dppm) ligands has been prepared. The complexes [Pd 2R 2(μ-H) (μ.-dppm) 2 ] PF 6 (R = Me, Et, Bu, CH 2SiMe 3, Ph) were generated by reduction, using NaBH 3CN, of the corresponding halide-bridged species. The products are thermally stable, yellow solids, and they have been characterized by 1H and 31P[ 1H] NMR spectroscopy. The ethyl complex [Pd2Et2(μ-H) (μ-dppm)2]PF 6 has been characterized further by X-ray crystallography. It crystallizes in the monoclinic space group P21 lc with a=10.6160 ( I ), 6=12.8637 (1 ), c=25.3739 (3) A, β=97.479 (1 )° and Z=2. The cation adopts an A-frame structure, with a Pd-Pd distance of 2.9933 (7) Å.

Di- and trinuclear complexes of palladium with a triphosphine ligand, bis(diphenylphosphinomethyl)phenylphosphine

Reaction of [Pd 2(RNC) 6](PF 6) 2 with dpmp (2 equiv.) generated dipalladium complexes, [Pd 2(dpmp) 2(RNC) 2](PF 6) 2 ( 1), in good yields, where R = 2,6-xylyl (Xyl) and 2,4,6-mesityl (Mes), Complex 1a (R = Xyl) was characterized by X-ray crystallography to have a metal-metal bonded dinuclear structure (Pd−Pd = 2.607(2) Å) without bridging ligand. The dpmp ligand chelates to the metal through only the terminal phosphorus atoms. Complex 1a in acetonitrile easily lost one isocyanide ligand and was transformed into a dpmp-bridged dipalladium complex, anti-[Pd 2(μ-dpmp) 2(XylNC)] (PF 6) 2 · CH 3CN (( 2a)CH 3CN). The dinuclear core of 2a consists of a three- and a four-coordinate Pd atom bridged by two dpmp ligands (Pd−Pd = 2.702(1) Å). Complex la was restored by treatment of 2a with an excess of XylNC. When compound 1 was treated with zero-valent palladium complex [Pd 3(RNC) 6], A-frame trinuclear complex, A-frame-[Pd 3(μ-dpmp) 2(RNC) 2](PF 6) 2 ( 4), was obtained. The trimer 4 was also prepared by the reaction of [Pd 3(RNC) 8](PF 6) 2 with dpmp (2 equiv.) via a linear dpmp-bridged trimer, linear-[Pd 3(μ-dpmp) 2(RNC) 2](PF 6) 2 ( 3). Complex 4a (R = Xyl) was analyzed by X-ray crystallography to be a trinuclear A-frame structure joined by two Pd−Pd σ-bonds (Pd−Pd = 2.592(2) Å, Pd−Pd−Pd = 79.19(8)°). The two dpmp ligands doubly bridge between the three metal atoms. Whereas, complex 4 was thermally and chemically stable, complex 3a (R = Xyl) reacted with I 2 to lead to a trinuclear Pd(II) complex, [{PdI 2(dpmp) 2)2PdI 2] ( 5), which was characterized by an X-ray analysis. The two cis-PdI 2(dpmp) units were joined by trans-PdI 2 fragment without metal-metal bonds.

Asymmetrical A-Frame Triplatinum Clusters Bridged by Small Organic Molecules and Bis((diphenylphosphino)methyl)phenylphosphine.

Reactions of the linear triplatinum complex [Pt(3)(&mgr;-dpmp)(2)(XylNC)(2)](2+) (3) with small organic molecules led to formation of asymmetrical A-frame triplatinum complexes with an additional bridge across one of the metal-metal bonds, where dpmp is bis((diphenylphosphino)methyl)phenylphosphine. Reaction of complex 3 with electron deficient alkynes (R(1)C&tbd1;CR(2): R(1) = R(2) = CO(2)Me; R(1) = H, R(2) = CO(2)Me; R(1) = R(2) = CO(2)Et) afforded a new series of triplatinum clusters formulated as [Pt(3)(&mgr;-dpmp)(2)(&mgr;-R(1)CCR(2))(XylNC)(2)](PF(6))(2) (5a, R(1) = R(2) = CO(2)Me; 5b, R(1) = H, R(2) = CO(2)Me; 5c, R(1) = R(2) = CO(2)Et) in good yields. The complex cation of 5b was characterized by X-ray crystallography to have an asymmetrical A-frame structure comprising three Pt atoms bridged by two dpmp ligands, in which an acetylene molecule was inserted into one of the Pt-Pt bonds (triclinic, P&onemacr;, a = 19.507(3) Å, b = 20.327(4) Å, c = 14.499(4) Å, alpha = 107.69(2) degrees, beta = 102.08(2) degrees, gamma = 71.30(1) degrees, V = 5148 Å(3), Z = 2, R = 0.070, and R(w) = 0.084). The Pt-Pt bond length is 2.718(1) Å and the Pt.Pt nonbonded distance is 3.582(1) Å. Treatment of 3 with an excess of HBF(4).Et(2)O gave the asymmetrical cluster [Pt(3)(&mgr;-dpmp)(2)(&mgr;-H)(XylNC)(2)](BF(4))(3).CH(2)Cl(2) (6.CH(2)Cl(2)), in 61% yield, and a similar reaction with p-NO(2)C(6)H(4)NC led to the formation of [Pt(3)(&mgr;-dpmp)(2)(&mgr;-R(3)NC)(XylNC)(2)](PF(6))(2).CH(2)Cl(2) (7.CH(2)Cl(2)) in 94% yield (R(3) = p-NO(2)C(6)H(4)). Complexes 6 and 7 are assumed to have a single atom-bridged, asymmetrical A-frame structures. Reaction of the complex syn-[Pt(2)(&mgr;-dpmp)(2)(XylNC)(2)](2+) (1) with [MCl(2)(cod)] (M = Pt, Pd) gave the dimer-monomer combined trinuclear cluster [Pt(2)MCl(2)(&mgr;-dpmp)(2)(XylNC)(2)](PF(6))(2) (8a, M = Pt, 89%; 8b, M = Pd, 55%). The structure of 8a was determined by X-ray crystallography to be comprised of a metal-metal-bonded diplatinum core and a monomeric platinum center bridged by two dpmp ligands with a face-to-face arrangement (triclinic, P&onemacr;, a = 18.082(7) Å, b = 19.765(6) Å, c = 15.662(4) Å, alpha = 98.51(2) degrees, beta = 94.24(3) degrees, gamma = 109.82(2) degrees, V = 5161 Å(3), Z = 2, R = 0.069, and R(w) = 0.080). The Pt-Pt bond length is 2.681(2) Å and the Pt.Pt nonbonded distance is 3.219(2) Å. The heteronuclear complex 8b was transformed to an A-frame trinuclear cluster, [Pt(2)PdCl(&mgr;-Cl)(&mgr;-dpmp)(2)(XylNC)](PF(6))(2) (9), which was characterized by X-ray crystallography (monoclinic, C2/c, a = 33.750(9) Å, b = 28.289(9) Å, c = 23.845(8) Å, beta = 118.19(4) degrees, V = 20066 Å(3), Z = 8, R = 0.082, and R(w) = 0.077). The diplatinum unit (Pt-Pt = 2.606(2) Å) is connected to the mononuclear Pd center by a chloride bridge (Pt.Pd = 3.103(3) Å, Pt-Cl-Pd = 79.6(3) degrees ).