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991.
Aderval S. Luna Hugo Borges Pereira Iracema Takase Rodrigo Araújo Gonalves Ralph Edward Sturgeon Reinaldo Calixto de Campos 《Spectrochimica Acta Part B: Atomic Spectroscopy》2002,57(12):2047-2056
Volatile species of Ag, Cu, Cd, and Zn were generated at room temperature by the addition of sodium tetrahydroborate (III) to an acidified solution of the analytes. The vapor-phase species were rapidly transported to a pre-heated graphite tube, the surface of which was previously treated with Ir as a permanent chemical modifier. The volatile species were trapped at the Ir treated tube surface, and the further heating of the furnace permits their determination by atomic absorption spectrometry. A univariate approach was used to achieve optimized conditions and derive the figures of merit. The limits of detection based on a 3σb criterion were 10 (1); 0.006 (6×10−4); 28 (2.8) and 1.1 (0.11) ng (μg ml−1) for Ag, Cd, Cu and Zn, respectively. Precision of replicate measurements was typically approximately 10% R.S.D. Using a transfer line as short as possible should minimize losses of analyte during the transport to the graphite furnace. The overall efficiency of the volatile species generation and trapping process estimated for silver was 13%. 相似文献
992.
Electroless and electroplated nickel electrodes are extensively used for hydrogen evolution reaction (HER). In the present
work, TiO2-supported IrO2 mixed oxide composite was prepared and used to reinforce Ni–P electroless plates to be used as catalytic electrodes for HER.
The electrodes exhibited high electrocatalytic activity when the electrodes were used for HER. All the parameters including
particle size of the catalyst, surface roughness, and surface active sites were studied. The particle size of the IrO2 catalyst in the mixed oxide was found to have high influence on the catalytic activity of the electrodes. Low overpotential
as low as 70 mV at a current density of 200 mA cm−2 was achieved with the mixed oxide-reinforced Ni–P electrodes. 相似文献
993.
María P. García M. Victoria Jimnez Teresa Luengo Luis A. Oro 《Journal of organometallic chemistry》1996,510(1-2):189-195
The reaction of the anionic mononuclear rhodium complex [Rh(C6F5)3Cl(Hpz)]t- (Hpz = pyrazole, C3H4N2) with methoxo or acetylacetonate complexes of Rh or Ir led to the heterodinuclear anionic compounds [(C6F5)3Rh(μ-Cl)(μ-pz)M(L2)] [M = Rh, L2 = cyclo-octa-1,5-diene, COD (1), tetrafluorobenzobarrelene, TFB (2) or (CO)2 (4); M = Ir, L2 = COD (3)]. The complex [Rh(C6F5)3(Hbim)]− (5) has been prepared by treating [Rh(C6F5)3(acac)]− with H2bim (acac = acetylacetonate; H2bim = 2,2′-biimidazole). Complex 5 also reacts with Rh or Ir methoxo, or with Pd acetylacetonate, complexes affording the heterodinuclear complexes [(C6F5)3Rh(μ-bim)M(L2)]− [M = Rh, L2 = COD (6) or TFB (7); M = Ir, L2 = COD (8); M = Pd, L2 = η3-C3H5 (9)]. With [Rh(acac)(CO)2], complex 5 yields the tetranuclear complex [{(C6F5)3Rh(μ-bim)Rh(CO)2}2]2−. Homodinuclear RhIII derivatives [{Rh(C6F5)3}2(μ-L)2]·- [L2 = OH, pz (11); OH, StBu (12); OH, SPh (13); bim (14)] have been obtained by substitution of one or both hydroxo groups of the dianion [{Rh(C6F5)3(μ-OH)}2]2− by the corresponding ligands. The reaction of [Rh(C6F5)3(Et2O)x] with [PdX2(COD)] produces neutral heterodinuclear compounds [(C6F5)3Rh(μ-X)2Pd(COD)] [X = Cl (15); Br (16)]. The anionic complexes 1–14 have been isolated as the benzyltriphenylphosphonium (PBzPh3+) salts. 相似文献
994.
The extraction of rhodium and iridium with 4-(non-5-yl)pyridine (NP) was investigated. The rate of rhodium extraction increases with increasing concentration of NP and chloride ions. Spectroscopic studies indicate that the extracted species is an ion pair, RhCl3?6 3HNP+. Under the conditions of optimum Rh extraction ([Cl?]=3.7 M, [NP]=0.3 M, [H]=0.08 M), iridium is also extracted by NP with similar efficiency in the form of IrCl3?6 3HNP+. The use of hypophosphorous acid to labilize rhodium results in a better extraction of rhodium without significantly changing the extraction of iridium. The efficiency and kinetics of the rhodium extraction improve with increasing chloride concentration. For [Cl?] ? 3.7 M, [H3PO2]=2.5 M, [NP]=0.3 M and Ph ≈ 1.6, 82% of rhodium is extracted in 4 min and 95% in 30 min. 相似文献
995.
Nigel T. Lucas Ian R. Whittall Mark G. Humphrey David C.R. Hockless M.P. Seneka Perera Michael L. Williams 《Journal of organometallic chemistry》1997,540(1-2):147-154
Reactions of CpMoIr3(μ-CO)3(CO)8 (1) with stoichiometric amounts of phosphines afford the substitution products CpMoIr3(μ-CO)3(CO)8−x (L)x (L = PPh3, x = 1 (2), 2 (3); L = PMe3, x = 1 (4), 2 (5), 3 (6)) in fair to good yields (23–54%); the yields of both 3 and 6 are increased on reacting 1 with excess phosphine. Products 2–5 are fluxional in solution, with the interconverting isomers resolvable at low temperatures. A structural study of one isomer of 2 reveals that the three edges of an MoIr2 face of the tetrahedral core are spanned by bridging carbonyls, and that the iridium-bound triphenyiphosphine ligates radially and the molybdenum-bound cyclopentadienyl coordinates axially with respect to this Molr2 face. Information from this crystal structure, 31P NMR data (both solution and solid-state), and results with analogous tungsten—triiridium and tetrairidium clusters have been employed to suggest coordination geometries for the isomeric derivatives. 相似文献
996.
The pyrolysis of hydrated bis(pyrazinecarboxylate)copper(II) under an argon atmosphere proceeds via the loss of the water molecules at 84–95°C, ΔH=40.4 kJ (mol H2O)?1 followed by the thermal decomposition of the complex at 284–325°C, ΔH=97.0 kJ·mol?1, yielding 0.72 mole of pyrazine, 0.28 mole of bipyrazine, and 2 mole of CO2 per mole of complex. 相似文献
997.
O. Gropen M. Sjøvoll H. Strømsnes E. Karlsen O. Swang K. Fægri Jr 《Theoretical chemistry accounts》1994,87(4-5):373-385
Summary Relativistic effective core potential calculations have been carried out for the reactions of Pt, Os, Ir, and Re with H2. The calculations demonstrate the importance of a singly occupied 6s orbital for forming a strong bond. Pt and Ir have low-lying states with such occupancy, whereas Os and Re only attains this through a rather costly excitation. In consequence, the reaction barriers are considerably smaller for Pt and Ir than for Os and Re. 相似文献
998.
The reaction of [{Ir(cod)(μ‐Cl)}2] and K2CO3 or of [{Ir(cod)(μ‐OMe)}2] alone with the non‐natural tetrapyrrole 2,2′‐bidipyrrin (H2BDP) yields, depending on the stoichiometry, the mononuclear complex [Ir(cod)(HBDP)] or the homodinuclear complex [{Ir(cod)}2(BDP)]. Both complexes react readily with carbon monoxide to yield the species [Ir(CO)2(HBDP)] and [{Ir(CO)2}2(BDP)], respectively. The results from NMR spectroscopy and X‐ray diffraction reveal different conformations for the tetrapyrrolic ligand in both complexes. The reaction of [{Ir(coe)2(μ‐Cl)}2] with H2BDP proceeds differently and yields the macrocyclic [4e?,2H+]‐oxidized product [IrCl2(9‐Meic)] (9‐Meic = monoanion of 9‐methyl‐9,10‐isocorrole), which can be addressed as an iridium analog of cobalamin. 相似文献
999.
《Electroanalysis》2003,15(12):1043-1053
The redox chemistry of the stable tetracoordinated 16 valence electron d8‐[Ir+I(troppPh)2]+(PF6)? and pentacoordinated 18 valence d8‐[Ir+I(troppPh)2Cl] complexes was investigated by cyclic voltammetry (troppPh=dibenzotropylidenyl phosphine). The experiments were performed using a platinum microelectrode varying scan rates (100 mV/s–10 V/s) and temperatures (? 40 to 20 °C) in tetrahydrofuran, THF, or acetonitrile, ACN, as solvents. In THF, the overall two‐electron reduction of the 16 valence electron d8‐[Ir+I(troppPh)2]+(PF6)? proceeds in two well separated slow heterogeneous electron transfer steps according to: d8‐[Ir+I (troppPh)2]++e?→d9‐[Ir0(troppPh)2]+e?→d10‐[Ir?I(troppPh)2]?, [ks1=2.2×10?3 cm/s for d8‐Ir+I/d9‐Ir0 and ks2=2.0×10?3 cm/s for d9‐Ir0/d10‐Ir?I]. In ACN, the two redox waves merge into one “two‐electron” wave [ks1,2=7.76×10?4 cm/s for d8‐Ir+I/d9‐Ir0 and d9‐Ir0/d10‐Ir?I] most likely because the neutral [Ir0(troppPh)2] complex is destabilized. At low temperatures (ca. ? 40 °C) and at high scan rates (ca. 10 V/s), the two‐electon redox process is kinetically resolved. In equilibrium with the tetracoordianted complex [Ir+I(troppPh)2]+ are the pentacoordinated 18 valence [Ir+I(troppPh)2L]+ complexes (L=THF, ACN, Cl?) and their electrochemical behavior was also investigated. They are irreversibly reduced at rather high negative potentials (? 1.8 to ? 2.4 V) according to an ECE mechanism 1) [Ir+I(troppPh)2(L)]+e?→[Ir0(troppPh)2(L)]; 2) [Ir0(troppPh)2(L)]→[Ir(troppPh)2]+L, iii) [Ir0(troppPh)2]+e?→[Ir?I(troppPh)2]?. Since all electroactive species were isolated and structurally characterized, our measurements allow for the first time a detailed insight into some fundamental aspects of the coordination chemistry of iridium complexes in unusually low formal oxidation states. 相似文献
1000.
John B. Claridge Ralph C. Layland Richard D. Adams Hans-Conrad zur Loye 《无机化学与普通化学杂志》1997,623(7):1131-1134
NaCa3IrO6 ( I ) and NaCa3RuO6 ( II ) crystallize with trigonal (rhombohedral) symmetry in the space group R3 c, Z = 6, for I a = 9.272(3) Å, c = 11.214(1) Å; for II a = 9.244(3) Å, c = 11.201(1) Å. NaCa3IrO6 ( I ) and NaCa3RuO6 ( II ) are isotypic to compounds of the Sr4PtO6 structure type. The structures have been solved by means of single crystal X-ray diffraction data analysis with the reliability factors for I of R = 0.032 and Rw = 0.039; and the the reliability factors for II of R = 0.024 and Rw = 0.031. The structure consists of infinite chains of alternating face-sharing MO6 octahedra, where M?Ir or Ru, and NaO6 trigonal prisms. The chains are separated by the calcium cations. 相似文献