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Abstract: The mechanism of the iridium-catalyzed functionalization of a primary C-H bond at the γ position of an alcohol (5) is investigated by density functional theory (DFT) calculations. A new [...]

Mixed-valence ruthenium (Ru[O.sub.x]) and iridium (Ir[O.sub.x]) oxides and composites on their basis (Ru[O.sub.x]-Ir[O.sub.x] or Ir[O.sub.x]-Ru[O.sub.x]) electrodeposited onto the surface of a glassy carbon electrode exhibit a catalytic activity in the electrooxidation of uric acid, xanthine, and hypoxanthine. The transition from metal oxides to composites of two mixed-valence metal oxides leads to an increase in the catalytic effect of the oxidation of hydroxypurines. The Ir[O.sub.x]-Ru[O.sub.x] composite demonstrated the highest catalytic activity. Procedures for the amperometric detection of hydroxypurines on this composite electrode under the conditions of flow-injection analysis (FIA) and sequential injection analysis are proposed. A linear dependence of an analytical signal on the analyte concentration is observed in the range 1 x [10.sup.-6] to 5 x [10.sup.-3] M for uric acid and xanthine and 5 x [10.sup.-7] to 5 x [10.sup.-3] M for hypoxanthine under FIA conditions and from 5 x [10.sup.-7] to 5 x [10.sup.-3] M for uric acid and xanthine and 5 x [10.sup.-8] to 5 x [10.sup.-3] M for hypoxanthine in sequential injection analysis. Under FIA conditions, the sensitivity, rapidity, and performance of the analysis increase compared to the stationary conditions. The advantages of sequential injection analysis over FIA include a lower consumption of the supporting electrolyte; the absence of pumps and connections; and an increase in sensitivity, reproducibility, and rapidity. Keywords: chemically modified electrodes, mixed-valence ruthenium and iridium oxides, electrooxidation of hydroxypurines, flow injection analysis, sequential injection analysis DOI: 10.1134/S106193481409010X, Hydroxypurines--hypoxanthine (HX), xanthine (X), and uric acid (UA)--are products of the metabolism of purine bases. The control of the concentration of these substances in biological fluids facilitates the diagnostics of [...]

Density functional theory (DFT) is used to explore the competitive C--H and C--Cl oxidative additions (OA) of chlorobenzene to the cationic Ir(I) complex: [[(PNP*)[Ir.sup.I]].sup.+] [PNP* = 2,6- bis((dimethylphosphino)methyl)pyridine]. Consistent with [...]

The mechanism for triplet energy transfer from the green-emitting fac-tris[2-(4'-tert-butylphenyl)pyridinato]-iridium (Ir[(tBu-ppy).sub.3]) complex to the red-emitting bis[2-(2'-benzothienyl)pyridinato-N,[C.sup.3')(acetylacetonato)-iridium (Ir[(btp).sub.2](acac)) phosphor is reported. The findings suggest that the triplet energy transfer occurs via the Forster mechanism when the transition dipole moments involved on energy donor and acceptor are not neglible.

Abstract -- The kinetics of noncatalytic and catalytic oxidation reactions of 4-amino-4'-methoxydiphenylamine with different oxidants in aqueous solutions and in the presence of surfactants was studied. The catalytic activity of [...]

The deuterium NMR spectra of the ternary metal deuterides (TMDs) [Ca.sub.2]Rh[D.sub.5] and [Ca.sub.2]Ir[D.sub.5] has shown that the disorder is dynamic at room temperature. The differential scanning calorimetric study of the transition in [Ca.sub.2]Ir[H.sub.5] has located a reversible phase transition at 284 K with an enthalpy change of 650 J [mol.sup.-1] and entropy change of 2.3 J [K.sup.-1] [mol.sup.-1].

A study to examine the catalytic properties of small clusters of rhodium and of iridium on oxide supports using the hydrogenation reaction of ethene, propene, and toluene was conducted. The results indicated self-inhibition of reaction adsorbed hydrocarbons and differences between ethene hydrogenation and propene hydrogenation that may arise primarily from different adsorbate-adsorbate interactions.

Abstract -- The formation of ion pairs of Rh(III) and Ir(III) with pyruvic acid acylhydrazones and symmetric cyanine dyes, derivatives of 1,3,3-trimethyl-3H-indolium, was studied. It was demonstrated that rhodium and [...]

The intrinsic gas-phase stability of the IrCl6(super 3 -) trianion and its microsolvated clusters, IrCl6(super 3 -).(H2O)(sub n) n = 0-10, is investigated. Calculations indicate that the bare trianion is metastable with respect to decay via both electron detachment and ionic fragmentation.

An efficient methodology is developed for the reductive alkylation of secondary amine with aldehyde and Et(sub 3)SiH using an iridium complex as a catalyst. A variety of secondary amines could be alkylated by allowing them to react with aldehydes and polymethylhydrosiloxane in the presence of an iridium catalyst to afford the corresponding tertiary amines in excellent yields.

The assembly of Ir4(Co)12 from Ir(CO)2(acac) precursors in the supercages of the zeolite NaY is investigated by extended X-ray absorption fine structures (EXAFS) and in-situ infrared (IR) spectroscopies. The results revealed that conditions of pretreatment of the zeolite significantly affect the chemistry of the intercage cluster assembly of Ir4(Co)12 in zeolites nanopores.

The photoluminescence (PL) dynamics of Ir(ppy)(sub 3)-cored dendrimers with the simple molecule Ir(ppy)(sub 3) in solution, blends, and neat films are discussed. Extensive aggregation of Ir(ppy)(sub 3) molecules is indicated by their rough surface with aggregated region of rodlike structure, as obtained by atomic force microscopy, which suggests that the PL quenchers in neat Ir(ppy)(sub 3) films may be excimers.

It is found that incorporation of SnO2 and Sb2O5 into IrOx not only saved the precious content significantly but also generated a synergic effect to make Ti/IrOx-Sb2O5-SnO2 much more stable. Ternary IrOx-Sb2O5-SnO2 is a promising electocatalyst for O2 evolution.

The nanosized Rulr bimetallic clusters in the NaY zeolite show strong resistance for the agglomeration in 1-atm oxygen and at high temperatures, compared to the Ru/NaY. Nanosized Rulr bimatallic clusters containing of 30-60 atoms can be obtained from the thermal decomposition and reduction with hydrogen of the precursor zeolite containing Ru complex and Ir (NH3)5(H2O)3+ free of chloride.

A general approach is developed for the numerical simulation of square wave anodic stripping voltammetry at hemispherical and uniform planar electrodes based on the backward implicit method. Data is presented for the nature of mercury on the surface of both iridium and copper substrates, obtained by atomic force microscopy.

The citrate-stabilized IrO2 colloid was self-assembled onto an indium tin oxide (ITO) electrode to form a monolayer of the colloidal IrO2 particles when dipped in the colloidal solution. The self-assembly could be achieved by a chemical interactions between carboxylate groups on the citrate stabilizer and hydroxyl groups on the ITO surface to form ester bonds.

Ir-catalyzed allylic substitutions is used to prepare chiral 1,6-enynes with very high diastereoselectivity induced by a chirality center of the enyne. Platinum(II) chloride-catalyzed domino enyne isomerization/Diels-Alder reaction is found to provide stereoselective access to complex heterocycles.

The enantioselective ring-opening reactions of azabicyclic alkenes with primary and secondary aromatic amine nucleophiles are described by using an iridium catalyst generated in situ from [[Ir(COD)Cl].sub.2] and (S)-BINAP. The reaction has produced the corresponding trans-1,2-diamine derivatives and trans-configuration of the 1,2-diamino product is conformed by X-ray crystallography.

[[Ir(COD)Cl].sub.2]/Phosphoramidite ligand system is used for developing an allylic substitution of O-allyl carbamothioates. The reaction has proceeded in the favor of branched products, which has produced chiral S-allyl carbamothioates.

A nucleophilic substitution of propargylic alcohols with carbon, sulfur, oxygen and nitrogen nucleophiles is shown by using a high-valent [[Ir(COD)(Sn[Cl.sub.3])Cl([mu]-Cl)].sub.2] catalyst in 1,2-dichloroethane to produce the corresponding propargylic products. Alkyl or aryl substituted tertiary propargylic alcohols have produced substituted indenes with bulky arenes through allenylic intermediate and an electrophilic mechanism is described from Hammett correlation.

The ester-directed regioselective borylation of arenes catalyzed by a silica-supported monophosphine-Ir complex has exhibited a broad substrate scope toward heteroaromatic compounds, including thiophene, pyrrole, furan, benzothiophene, benzofuran, indole, and carbazole derivatives. The regioselectivity is complementary to the selectivities in the heteroarene C-H borylation with the dtbpy-Ir catalyst system.

The preparation of [omega]-hydroxy carboxylic acids and [alpha],[omega]-dimethyl diketones is achieved by using [alpha],[omega]-diols as alkylating agents under the affect of an iridium catalyst. The alkylation of acetone with 1,10-decanediol in the presence of [[IrCl(cod)].sub.2] and KOH has resulted in a muscone precursor, 2,15-hexadecanedione (HDDO).

5-Substituted-2-furan methanols are subjected to enantioselective carbonyl allylation, crotylation and tert-prenylation after exposing to allyl acetate, [alpha]-methyl allyl acetate, or 1,1-dimethylallene in the presence of an ortho-cyclometalated iridium catalyst modified by (R)-Cl,MeO-BIPHEP, (R)-C3-TUNEPHOS and (R)-C3-SEGPHOS. Optically enriched products of carbonyl allylation, crotylation and reverse prenylation are subjected to Achmatowicz rearrangement for producing the corresponding [gamma]-hydroxy-[beta]-pyrones, with negligible erosion of enantiomeric excess.

A complex of [[Ir(OMe)(cod)].sub.2] and 4,4-di-tert-butyl-2,2-bipyridine (dtbpy) has catalyzed the Z-selective, dehydrative silylation of terminal alkenes, but not 1,2-disubstituted alkenes, with triethylsilane or benzyldimethylsilane in THF. Yields and Z-stereoselectivity are improved by 2-norbornene, whereas [alpha],[beta]-unsaturated esters are unreactive and the reaction has proceeded through a Heck-type mechanism.

The application of the various Boc groups as the protectors and directors of the Ir-catalyzed C-H borylation of the various heterocycles is discussed. The results prove that thermolysis can also be employed for the removal of the Boc group.

The article discusses the mechanisms involved in the carbon-carbon bond formation reaction, which is shown to be based on the carbon-hydrogen bond functionalization of the unactivated alkenes. The cyclic alkenes are shown to play an extremely significant role in determining the selectivity of the discussed bond functionalization.

Mono- and 2,2E-disubstituted terminal alkenes are isomerized into the more stable internal (Z)- and (E)-alkenes by treating them with catalytic amounts of [[(allyl)PdCl].sub.2] or [[(allyl)NiBr].sub.2], a triarylphosphine, and silver triflate at room temperature. The reaction is tolerant to a wide variety of functional groups including other reactive olefins and unlike the more reactive Ir catalysts, monosubstituted alkenes has given almost exclusively the 2-alkenes.

The first 11 step synthesis of the natural product (+)-mutisianthol to yield 21 percent overall yield from 2-methylanisole, which involved the asymmetric hydrogenation of a nonfunctionalized olefine using chiral iridium as catalyst and the ring contraction of 1,2-dihydronapthalenes is described. The target molecules showed moderate activity against the human tumor cell lines SF-295, HCT-8, and MDA-MB-435.

A facile iridium-catalyzed N-heterocyclization of naphthylamines with diols is used to synthesize benzoquinonline derivatives. The ligand influenced N-heterocyclization reaction could also be used to obtain benzoindoles.

The studies regarding an unusual isomerization-cyclization sequence mediated by an iridium species derived from Crabtree's catalyst is reported. The key steps in the process involve initial Ir(I)-mediated isomerization of the alkene to form an N-sulfonyl enamine followed by cyclization.

The report explains the synthesis and electrophosphorescence of a new deep red phosphorescent Ir(III) complex, which is commonly used in polymer light-emitting diodes. These substances can easily solubalize arylsilyl-substituted ligands, exhibiting excellent phase homogeneity.

Narrow-line emission and excitation spectra of the lowest triplet state are studied in a Shpol'skii host (n-octane) for three cyclometalated Ir[L.sub.2]acac complexes. The spectra permit the evaluation of most of the splittings among the triplet sublevels and exhibit informative Zeeman effects, while the broadband emission of the complexes in poly(methyl methacrylate), combined with the Shpol'skii data, yield the one remaining splitting as well as properties of the individual sublevels, that is, radiative and nonradiative decay rates and emission spectra.

Some new types of nonclassical iridium carbonysis formed after CO adsorption on Ir-ZSM-5 are reported. An investigation is conducted based on a Fourier transform infrared spectroscopy and the results are explained by the smaller cationic radius of [Ir.sup.2+], which is associated with a decease of the number of ligands required for coordinative saturation.

The syntheses of bright deep blue emitting mixed ligand Ir(III) complexes comprising two cyclometalating, one phosphine and one cyano, ligands are reported. A firm connection between the nature of the excited states and the physicochemical behavior of the complexes with the different ligand systems is elucidated by correlating the observed crystal structures, spectroscopic properties and electrochemical properties with the theoretical results obtained by the density functional theory (DFT) methods.

The iridium complex-catalyzed cycloaddition of diynes with monoynes and monoenes is developed. The [2+2+2] cycloaddition of alpha,omega-diynes with monoynes and monoenes and also a novel aromatization reaction of alpha,omega-diynes with monoenes is reported.

Adsorption and reactions of NO on clean and CO-precovered Ir(111) were investigated by means of X-ray photoelectron spectroscopy (XPS), high-resolution electron energy loss spectroscopy, infrared reflection absorption spectroscopy and temperature-programmed desorption. Two NO adsoprtion states, indicative of fcc-hollow sites and atop sites, were present on the Ir(111) surface at saturation coverage.

A 3-parameter local hot spot model of gas-surface reactivity is employed to analyze and predict dissociative sticking coefficients for CH4 incident on Ir(111) under varied nonequilibrium and equilibrium conditions. The CH4 dissociative sticking coefficient predicted for Ir(111) surfaces at thermal equilibrium, based on the molecular beam experiments, is roughly four orders of magnitude higher and suggests that substaintial improvements in catalyst turnover rates may be possible.

The kinetic energy dependence of reactions of the late third-row transition metal cation Ir(super +) with H2, D2, and HD is measured using a guided ion beam tandem mass spectrometer. Ir(super +) was found to have a stronger M(super +) -H bond, which can be explained by the lanthanide contraction and relativistic effects that alter the relative size of the valence s and d orbitals.

The utility of a novel class of P,N-ligands incorporating a chiral sulfinyl imine moiety is demonstrated in the iridium-catalyzed hydrogenation of both functionalized and unfunctionalized olefins. The modularity of the P,N-sulfinyl ligand class is highlighted by the facile preparation of a variety of sterically and electronically different ligands.

The adsorption and reaction of acetylene on planar and faceted Ir(210) were studied utilizing temperature-programmed desorption (TPD), Auger electron spectroscopy (AES), low-energy electron diffraction (LEED), and high-resolution electron energy loss spectroscopy (HREELS). The evidence was found in TPD measurements for structure sensitivity in decomposition of acetylene over the clean faceted Ir(210) surface versus the clean planar Ir(210) surface, which is attributed to nanometer sale structures on the faceted surface.

The theoretical studies of electronic structures and related chemical properties of isoelectronic complexes M(bpy)(sub 3)(super n+) (M=Re, Os and Ir; n=1,2, and 3, respectively) are carried out with density functional theory (DFT) method at B3LYP/LanL2DZ level.

Research is done on laser-ablated rhodium and iridium atoms, which are reacted with nitric oxide and the products, are isolated in solid neon and argon. In conclusion, the stretching frequencies observed for the isolated nitrosyls are close to those for analogous nitrosyl species on rhodium and iridium surfaces, which will aid in interpreting vibrational data for surface species.