Iridium oxide, single crystals

The BINAP derivative of the ort/io-cyclometallated iridium catalyst has been characterized by single crystal X-ray diffraction analysis [280]. Remarkably, although the reaction sequence depends upon oxidation of either the reactant alcohol or isopropanol, the enantiomeric purity of the homoallylic alcohol product... 

The catalytic oxidation of CO on iridium has not been as extensively studied as with palladium and platinum. However, as for these metals, both steady-state (40, 54, 124, 199-202) and nonsteady-state investigation (124, 200-203) have been carried out on both polycrystalline and single crystal surfaces. As the results are for the most part very similar to those obtained on palladium and platinum surfaces, only those results that shed additional light on the kinetics and mechanism basic to the reaction will be emphasized here. 

Hexachloroiridates(IV) may be prepared by (i) chlorinating a mixture of iridium powder and an alkali metal chloride (ii) in solution, by the addition of an alkali metal chloride to a suspension of hydrous Ir02 in aqueous HC1 or (iii) by the oxidation of [IrCl ] " by O2 in acidic media. Oxidation by Oj probably occurs via reaction (122), with = + 0.21 V. Fine" has suggested that the reverse of reaction (122) occurs in alkaline media. The black crystalline sodium salt Na2[IrCls] is water soluble, and is the usual starting material for the synthesis of other iridium(IV) coordination complexes. The resonance Raman spectrum of (NBu4)2[IrCle] reveals anomalous polarization of all bands this has been ascribed to Jahn-Teller distortions present in the excited electronic state. The single-crystal electronic spectra of various [IrCl ] " salts have also been reported." ... 

In order to be able to properly examine the inherent activity of minute amounts of OER catalysts, one needs a substrate with minimal interference, extremely slow OER kinetics of its own and extraordinary stability at high positive electrode potentials. The unique featiues of 3M s Pt-NSTF (nanostructured thin film) catalyst [12] such as superior durability, electrochemical inertness at high potentials, and the absence of corrosion interference due to exposed carbrui, made it a logical choice as a support [13, 14]. It is well known that pure platinum has a high overpotential for OER. For instance, at a current density of 1 mA/cm, the OER on platinum proceeds at a potential that is 0.47 V higher than oti single crystal ruthenium oxide [15]. Thus, the OER partial current density oti the Pt-NSTF substrate wiU be orders of magnitudes lower than on ruthenium, iridium, and other similar OER-active materials. 

Berlowitz PJ, Peden CHF, Goodman DW (1988) Kinetics of carbon monoxide oxidation on single-crystal palladium, platinum, and iridium. J Phys Chem 92 5213-5221... 

Dihalodicarbonyl iridium compounds constitute an important class of chain compounds. These compounds are synthesized by treating K2lrXg with CO under pressure or heating in formic acid. Single crystal study of Pr(CO)2Cl2] revealed a chain structure. Alkah metal counterions compensate the charge. The fractional oxidation states of iridium in this series vary in the small range of -1-1.39 to -1-1.44. " These compounds exhibit metallic copper luster and metal-like conductivity. 

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