- Ni[TCNE]2 · zCH2Cl2 (Tc = 13 K) and VxNi1-x[TCNE]y · zCH 2Cl2 solid solution room temperature magnets
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Magnetically ordered Ni[TCNE]2 · zCH2Cl 2 (Tc = 13 K) is reported for the first time from the reaction of Ni(CO)4 with tetracyanoethylene (TCNE). A family of new solid solution room temperature magnets of VxNi1-x[TCNE] y · zCH2Cl2 (0 ≤ x II for VII in V[TCNE]y · zCH 2Cl2 does not alter the Tc significantly for x ≥ 0.05 and does not alter Hcr significantly for x > 0; however, the magnitude of M increases with x, as does the broadness of the peaks in the χ′(T) and χ″(T) ac susceptibilities. Hence, the magnetic properties of the room temperature V[TCNE]y · zCH 2Cl2 magnet can be finely tuned via synthetic chemistry methodology, making this material more amenable in future technologies.
- Vickers, Elaine B.,Senesi, Andrew,Miller, Joel S.
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- D3d ground-state structure of V(CO)6: A combined matrix isolation and ab initio study of the Jahn-Teller effect
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Structures, relative energies, vibrational spectra, and ESR parameters of the 17e- molecule V(CO)6 in Oh, D3d, D4h, and D2h symmetry have been computed with density functional and high-level ab initio methods. At all theoretical levels applied, the same energetic order is obtained, D3d 2h 4h h, with the D2h structure as a transition state connecting equivalent D3d species. At the RCCSD(T)/AE2 level using UBP86/AE2 geometries, the energies of the D2h, D4h and Oh species relative to that of D3d minimum are predicted to be 210, 535, and 731 cm-1, respectively. According to molecular dynamics simulations on the UBP86/AE1 potential energy surface, the D3d minimum is preserved at very low temperatures (around 16 K), whereas at 300 K the molecule is highly fluxional with an averaged structure indistinguishable from that of [V(CO)6]- with its Oh symmetric ground state. Nearly complete IR and Raman spectra of V(CO)6 and V(13CO)6 have been recorded at 300 K for the first time in the gas phase, in solution, and at cryogenic temperatures in Ne and Ar matrices. The spectra show a pronounced temperature dependence, especially for the Jahn-Teller active modes, Eg and T2g. The observed infrared matrix spectra generally agree well with the calculated spectrum (BP86/AE2 level) for the D3d structure and much less with that of the D4h isomer. The A1g modes in the Raman spectra are reasonably well reproduced computationally in the harmonic approximation, whereas this approximation breaks down for the Eg and T2g bands, as expected. Further evidence for the D3d symmetry of V(CO)6 is obtained from a reanalysis of the experimental ESR spectrum that is reported in the literature. The observed ordering of the hyperfine coupling constants A∥ and A⊥ is reproduced theoretically only when distortion to D3d symmetry is assumed. In addition, the bonding properties of V(CO)6 are compared to those of [V(CO)6]- and Cr(CO)6.
- Bernhardt, Eduard,Willner, Helge,Kornath, Andreas,Breidung, Juergen,Buehl, Michael,Jonas, Volker,Thiel, Walter
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- Magnetic ordering in a vanadium-organic coordination polymer using a pyrrolo[2,3-: D:5,4- d ′]bis(thiazole)-based ligand
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Here we present the synthesis and characterization of a hybrid vanadium-organic coordination polymer with robust magnetic order, a Curie temperature TC of ~110 K, a coercive field of ~5 Oe at 5 K, and a maximum mass magnetization of about half that of the benchmark ferrimagnetic vanadium(tetracyanoethylene)~2 (V·(TCNE)~2). This material was prepared using a new tetracyano-substituted quinoidal organic small molecule 7 based on a tricyclic heterocycle 4-hexyl-4H-pyrrolo[2,3-d:5,4-d′]bis(thiazole) (C6-PBTz). Single crystal X-ray diffraction of the 2,6-diiodo derivative of the parent C6-PBTz, showed a disordered hexyl chain and a nearly linear arrangement of the substituents in positions 2 and 6 of the tricyclic core. Density functional theory (DFT) calculations indicate that C6-PBTz-based ligand 7 is a strong acceptor with an electron affinity larger than that of TCNE and several other ligands previously used in molecular magnets. This effect is due in part to the electron-deficient thiazole rings and extended delocalization of the frontier molecular orbitals. The ligand detailed in this study, a representative example of fused heterocycle aromatic cores with extended π conjugation, introduces new opportunities for structure-magnetic-property correlation studies where the chemistry of the tricyclic heterocycles can modulate the electronic properties and the substituent at the central N-position can vary the spatial characteristics of the magnetic polymer.
- Getmanenko, Yulia A.,Mullins, Christopher S.,Nesterov, Vladimir N.,Lake, Stephanie,Risko, Chad,Johnston-Halperin, Ezekiel
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- Voltammetric oxidation of solution and solid phases of salts of [V(CO)6]- in aqueous (electrolyte) media
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In the absence of water and oxygen the solution phase voltammetry of [V(CO)6]- in organic solvents exhibits an extremely well-defined, reversible, one-electron redox couple [V(CO)6]- ? V(CO)6+e-
- Bond,Colton,Mahon,Snook,Tan
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- Solvent enhancement of the magnetic ordering temperature (Tc) of the room temperature V[TCNE]x · S (S = solvent, TCNE = tetracyanoethylene; x ~ 2) magnet
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The reaction of V(CO)6 and TCNE in CH2Cl2, hexane, toluene (PhMe), and trifluoromethylbenzene (PhCF3) form an immediate black precipitate of V(TCNE)x · yS (S = solvent; x ~ 2; y ~ 0.5) composition, which have a magnetic ordering onset temperatures, Ton, in the range of 385-390 K (S = CH2Cl2, hexane, PhMe). For S = PhCF3 in addition to Ton being enhanced it exhibits greater thermal stability.
- Thorum, Matthew S.,Pokhodnya, Konstantin I.,Miller, Joel S.
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- Thin film Co[TCNE]2 and VyCo1-y[TCNE] 2 magnetic materials
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A chemical vapor deposition method has been developed for the synthesis of both solvent-free Co[TCNE]2 and VyCo1- y[TCNE]2 thin films. Both materials have been previously synthesized by solution metho
- Erickson, Preston K.,Miller, Joel S.
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- Chemistry of the vanadium-carbon σ Bond. 1. Insertion of carbon monoxide, isocyanides, carbon dioxide, and heterocumulenes into the V-C bond of tris(mesityl)vanadium(III)
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Complex 1, [V(Mes)3(THF)], reacts with ButNC to form the homoleptic tris(η2-iminoacyl) complex [V{η2-C(Mes)=NBut}3] (2), while the reaction with carbon monoxide leads to the elimination of MesC(O)Mes and reduction of vanadium to a vanadium-carbonyl species. Cyclohexyl and phenyl isocyanate groups insert into the three V-Mes bonds of 1, forming the tris(amido)derivatives [V{O-C(Mes)]=NCy}3], (6) and [V{O-C(Mes)=NPh}3] (7). Solvated forms of 7 were prepared, giving [py-V{O-C(Mes)=NPh}3] (8) and [MeCN-V{O-C-(Mes)=NPh}3] (9). Complex 1 undergoes a double insertion of CyN=C=NCy (Cy = C6H11), giving [{CyN-C(Mes)-NCy}2V(Mes)] (10) which undergoes a further insertion of CO or But-NC into the remaining V-Mes bond, forming [{CyN-C(Mes)-NCy}2V{η2-C(Mes)=O}] (11) and [{CyN-C(Mes)-NCy}2V{η2-C(Mes)=NBut}] (12), respectively. All complexes have a high-spin d2 configuration. The structures of 1, 2, 8, and 10 have been determined by X-ray analysis. Crystallographic details: 1 is monoclinic, space group P21/c, with a = 8.472(2) A? b = 14.273(4) A? c = 22.385(6) A?, α = γ = 90°, β = 97.64(3)°, Z = 4, and R = 0.057; 2 is triclinic, space group P1, with a = 17.913(2) A?, b = 13.697(2) A?, c = 8.273(1) A?, α = 80.40(1)°, β = 80.30(1)°, β = 88.34(1)°, Z = 2, and R = 0.070; 8 is triclinic, space group P1, with a = 14.701(1) A?, b = 14.808(1) A?, c = 13.267(1) A?, α = 69.06(1)°, β = 73.16(1)°, γ = 81.37(1)°, Z = 2, and R = 0.062; 10 is tetragonal, space group P41212, with a = 12.703(1) A?, b = 12.703(1) A?, c = 30.473(3) A?, α = β = γ = 90°, Z = 4, and R = 0.059.
- Vivanco, Marilin,Ruiz, Javier,Floriani, Carlo,Chiesi-Villa, Angiola,Rizzoli, Corrado
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p. 1794 - 1801
(2008/10/08)
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- Infrared spectroscopic study of the photochemical substitution and oxidative addition reactions of(η5-C5R5) M(CO)4 compounds of the group 5 metals: Characterization of the products of reaction with N2,H2, and HSiEt3-x Clx and the kinetic investigation of (η5-C5 R5)M(CO)
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IR spectroscopy has been used to study the photochemical reactions of H2 and N2 with CpM(CO)4 and Cp*V(CO)4 (Cp = η5-C5H5, Cp* = η5-C5Me5; M = V, Nb, and Ta) and of HSiEt3-xClx (x = 0, 2, and 3) with CpV(CO)4. The reactions have been studied by FTIR in liquid xenon solution (lXe) at ca. -80°C and by time-resolved IR spectroscopy (TRIR) in n-heptane solution at room temperature. In nearly all cases, UV irradiation leads to substitution of only one CO group. The only exceptions were the reactions of N2 with CpNb(CO)4 in lXe and with CpV(CO)4 in solid matrices at 20 K, where CpM(CO)2(N2)2 species were generated as secondary photoproducts. Reaction with H2 led to formation of nonclassical dihydrogen complexes CpV(CO)3(η2-H2), Cp*V(CO)3(η2-H2) and CpNb(CO)3(η2-H2), which was in thermal equilibrium with the classical dihydride CpNb(CO)3H2. v(H-H) IR bands have been observed for all three dihydrogen complexes. Reaction of CpTa(CO)4 with H2 led to oxidative addition and formation of CpTa(CO)3H2, which decayed over a period of 30 min in supercritical xenon solution at room temperature. IR data were also obtained for reaction with D2 and, in the case of V, with HD. IR spectra suggest that reaction of CpV(CO)4 with HSiEt3 results in the arrested oxidative addition to form a labile CpV-(CO)3(η2-H-SiEt3) complex, the first example of this type of compound of a group 5 metal. By contrast, reaction with HSiCl3 and HSiEtCl2 led to full oxidative addition, CpV(CO)3(H)SiR3. TRIR measurements showed that formation of all of these CpM(CO)3L species proceeds via a dissociative mechanism with transient formation of CpM(CO)3. CpV(CO)3 is ca. 100 times more reactive than its Nb and Ta analogs and nearly 1000 times more reactive than CpMn(CO)2 under similar conditions. Cp*V(CO)3 is even more reactive. Photoacoustic calorimetry (PAC) has been combined with TRIR to estimate V-(N2) and V-(η2-H2) bond dissociation enthalpies. The PAC results suggest that CpV(CO)3 interacts with the n-heptane solvent and is probably more correctly formulated as CpV(CO)3?(n-heptane). Finally, the reactions of V(CO)6 with N2 and with H2 were studied to compare the behavior of d5 vanadium. IR evidence was found for the formation of V(CO)5(N2) and V(CO)5(η2-H2) both in lXe and in n-heptane (TRIR). These compounds were significantly shorter lived than the corresponding CpV(CO)3L species under similar conditions. The photochemical formation of V(CO)5L occurred via V(CO)5, detected by TRIR, which was significantly less reactive toward CO, N2, and H2 than was CpV(CO)3.
- George, Michael W.,Haward, Mark T.,Hamley, Paul A.,Hughes, Catherine,Johnson, Frank P. A.,Popov, Vladimir K.,Poliakoff, Martyn
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p. 2286 - 2299
(2007/10/02)
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- Synthesis of hexacarbonyl derivatives of group 5 metals and electron-transfer processes. Crystal and molecular structure of tetracarbonyl(1,2-bis(diphenylphosphino)ethane)iodotantalum
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Vanadium, niobium, and tantalum hexacarbonylmetalate(-I) derivatives of several heterocyclic nitrogen bases, RnB[M(CO)6]n (R = H, Me; n = 1, 2), have been synthesized. In some cases an electron transfer from the hexacarbonylmetalate to the protonated or methylated BRnn+ cation has been observed. Pyridinium halides react with Na[M(CO)6] (M = Nb, Ta) in the presence of 1 equiv of 1,2-bis(diphenylphosphino)ethane (diphos) to give high yields of the halo tetracarbonyl derivatives MX(CO)4(diphos). The red-orange TaI(CO)4(diphos) complex has been studied by X-ray diffraction methods. Crystal data: space group P21/n; Mr 818.3; a = 14.864 (10) ?, b = 9.875 (7) ?, c = 19.335 (13) ?; β = 105.61 (2)°; U = 2733 (3) ?3; Z = 4; Dcalcd = 1.988 g cm-3; F(000) = 1568; μ(Mo Kα) = 52.4 cm-1. The geometry of the seven-coordinate tantalum atom is best described as a capped trigonal prism with the iodide ligand in the capping position. By reaction of Na[Ta(CO)6] with 1 equiv of hydrogen chloride and diphos in toluene, the hydride TaH(CO)4(diphos) has been isolated in good yield.
- Calderazzo, Fausto,Pampaloni, Guido,Pelizzi, Giancarlo,Vitali, Francesca
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p. 1083 - 1092
(2008/10/08)
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- Ring-Halogenated Carbonyl(η5-cyclopentadienyl)vanadium Complexes
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Hexacarbonylvanadium reacts with hexachloro- and hexabromocyclopentadiene to form the half-sandwich complexes (η5-C5X5)-V(CO)4 (X = Cl, 1; X = Br, 2).Complex 2 was characterized by X-ray structure analysis.With 1,2,3,4,5-pentachlorocyclopentadiene, (η5-C5HCl4)V(CO)4 (3) is formed along with 1.The reaction between 1,2,3,4-tetrachloro-6-phenylpentafulvene yields (η5-C5Cl4CH2Ph)V(CO)4 (4).Treatment of V(CO)6 with 1,1,3-trichloro- and -bromoindene results in the formation of 3,3'-dihaloindenyl-1-indenylidenes and small amounts of 5-(1,3-dichloroindenyl)>V(CO)4 (5). 1-bromo-1,2,3,4,5-penta phenylcyclopentadiene is debrominated to C5Ph5..
- Priebsch, Wolfgang,Hoch, Martin,Rehder, Dieter
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p. 1971 - 1976
(2007/10/02)
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- Carbonylvanadium Halfsandwich Complexes: Preparation, Structure, and 51V-NMR Spectra of Derivatives of η5-C5H5V(CO)4
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The reactions between V(CO)6 and alkylcyclopentadienes Cp'H yield a large number of halfsandwich complexes of the composition Cp'V(CO)4 I ( open Cp derivatives) and III (anellated Cp derivatives).The compounds are formed as by-products.The reactivity of the cyclopentadienes leading to the type III complexes drastically increases as the reactions are performed with Cp'Br (Cp = indenyl, fluorenyl).With acenaphthylene, azulene, and guaiazulene double-halfsandwich complexes 2 are obtained, which are present in solution in several meso forms.In the acenaphthylene complex one CO per Cp'V(CO)4 moiety can be replaced photochemically by PPh3.Doubly alkylated derivatives of type I form 1,2- and 1,3-isomers.The two diastereomeric pairs of enantiomes are observed in cases where there are two elements of chirality *N*, C5H5V(CO)2NN*>.Three centres of chirality *> yield four diastereomers.The differentiation of the isomers is performed on the basis of the 51V-NMR spectra. ?(51V) values span the range between -1534 and -1118 ppm , relative to VOCl3. η7-C7H7V(CO)3 (-1485 ppm) falls within this range, while shielding is clearly higher in 6-toluene-V(CO)4>(+) (-1660 ppm) than in the η5-Cp complexes.MeC(O)C5H4V(CO)4 (16), which can be obtained by Friedel-Crafts acylation, is reduced to the alcohol and converted into the oxime and phenylhydrazone.Force constants and band positions of the Cp'(CO)3(13CO) isotopomers of the type III complexes have been calculated.The crystal and molecular structures of C5H5V(CO)4 (refined determination) and 16 have been obtained from single crystal X-ray analyses.
- Hoch, Martin,Rehder, Dieter
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p. 1541 - 1552
(2007/10/02)
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- Arene-Metal Dimer Complexes (C6H6)2V2 and (C6H6)V2; Experiment and Xα Theory. 3
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V atoms have been shown in a previous paper (part 1) to react with one or two benzene rings in rare gas matrices to form the respective half-sandwich, (C6H6)V, or the bis(benzene)vanadium complex, (C6H6)2V, depending on the relative concentrations of the various components.In this study, at higher V atom loadings, the corresponding binuclear complexes (C6H6)V2 and (C6H6)2V2 are identified from a combination of a kinetic analysis and V atom concentration study, the results of thermal annealing, and the outcome of V and Cr atom depositions into low-temperature methylcyclohexane solutions of bis(toluene)M (M=V,Cr).Xα-SW calculations were undertaken to provide a qualitative insight into modes of bonding in metal dimer arene molecules.Simplified half-sandwich models were utilized in C6v and C2v symmetry, as implied by stable, known structural analogues.In both cases the molecular orbital divided neatly into three types.The first type related essentially to the benzene ligand itself.The second type was characterized by uniquely metal-metal bonding interactions.These interactions established a basis for inferring metal localized excitations as being at the origin of the electronic absorption spectra seen red-shifted from the main MLCT band.The third type detailed the metal-ligand bonding interactions.The C6v structure showed bonding interactions similar to those of the mono(benzene)vanadium half-sandwich.The C2v molecule showed features in common with metal atoms interacting with a benzene ring which can show latent allyl-like character.The relevance of such a structure to known vanadium dimer molecules incorporating a single fluxional benzene ring is indicated.
- Andrews, Mark P.,Ozin, Geoffrey A.
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p. 1245 - 1256
(2007/10/02)
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- PROTON- AND CARBONYL-MEDIATED ELECTRON TRANSFER PROCESSES FROM THE HEXACARBONYLVANADATE(-I) ANION
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Hexacarbonylvanadate(-I) derivatives of several heterocyclic nitrogen bases, BH+-, have been synthesized.The deep red volatile pyridinium derivative +-, was studied by X-ray diffraction methods and found to be tetragonal, space group I41/amd, with a 10.384(3), c 12.373(3) Angstroem and Z=4.Solution of the structure by the heavy-atom method followed by full-matrix least-squares refinement gave the final residuals (R=0.0450 and Rw=0.0442) for 180 unique observed reflections.Coordination about the vanadium atom, which lies at a site of local 42m symmetry, is octahedral due to two independent carbonyl groups.The pyridine moiety is disordered.The major feature of the molecular structure is the interaction of the nitrogen proton with the carbonyl oxigens of - inb the equatorial plane of the octahedron.The structural features are regarded as evidence in favour of the carbyne-type of structure for the C6HO6V precursor of V(CO)6 (C6HO6V -> 1/2 H2 + V(CO)6).Several substitution and redox processes involving the protonated nitrogen base derivatives have been observed, namely: (a) nitrogen base exchange; (b) dihydrogen evolution upon treatment with sodium metal; (c) electron-transfer from - to the nitrogen-bonded proton, with dihydrogen evolution; (d) electron-transfer from - to the cation with carbon-carbon coupling in the case of acridinium derivative.All the compounds reported are deeply coloured (the quinolinium derivative is black), suggesting the existence of a multicentre CO-mediated charge transfer from vanadium to the nitrogen base.
- Calderazzo, Fausto,Pampaloni, Guido,Lanfranchi, Maurizio,Pelizzi, Giancarlo
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- Metalcarbonyl Syntheses, XII. Tetracarbonyl(η5-pentamethylcyclopentadienyl)vanadium
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The hitherto unknown halfsandwich complex tetracarbonyl(η5-pentamethylcyclopentadienyl)vanadium (3) is easily accessible in 45 percent yield upon reaction of hexacarbonylvanadium (1) with pentamethylcyclopentadiene (2).Photolysis of 3 as well as reduction and subsequent protonation yield the dinuclear derivative 4 of composition (η5-C5Me5)2V2(CO)5.
- Herrmann, Wolfgang A.,Kalcher, Willibald
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p. 3886 - 3889
(2007/10/02)
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- SOME NEW RESULTS ON HEXACARBONYLS OF VANADIUM
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A new method for preparing V(CO)6, consisting of treating anhydrous and solvent-free NaV(CO)6 with dry HCl in a hydrocarbon solvent, is described.Evidence has been obtained that the reaction proceeds via the intermediate formation of an exceedingly unstable precursor of V(CO)6.No chemical or spectroscopic evidence was obtained for the presence in solution of hydridic vanadium species.The presence of stoichiometric amounts of water is sufficient to promote hydrogen transfer to form H3O(+)(-).
- Calderazzo, Fausto,Pampaloni, Guido,Vitali, Dario
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p. 455 - 458
(2007/10/02)
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