Iridium Compound Activates O and H - C&EN Global Enterprise (ACS

Nov 6, 2010 - A further understanding of how molecular oxygen and hydrogen are ... In earlier work, Dr. Vaska and J. W. Di-Luzio showed that the same ...
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ACTIVATION. Dr. Lauri Vaska studies activation of molecular oxygen and hydrogen by metal complexes. He finds that [IrCI(CO) (PhsP)?] activates both gases

Iridium Compound Activates 0 2 and H 2 Mellon workers isolate stable 0Q and H2 adducts of quadricovalent iridium complex A further understanding of how molec­ ular oxygen and hydrogen are acti­ vated by metal complexes and metals may result from the isolation of both the hydrogen and oxygen adducts of [IrCl(CO)(Ph,P)2]. The quadricovalent iridium com­ pound has recently been found to re­ versibly take up molecular oxygen in solution. The finding adds iridium to the small group of metals (such as iron and cobalt) that have previously been known to function as oxygen carriers in some of their complexes, according to Dr. Lauri Vaska of Mel­

lon Institute, Pittsburgh, Pa. In earlier work, Dr. Vaska and J. W. DiLuzio showed that the same iridium compound also reacts reversibly with hydrogen under normal conditions. Oxygen carriers show promise in some commercial processes. Such chelates were evaluated as potential oxygen sources for welding and cut­ ting during World War II. The cost of producing oxygen from air by cobalt carriers did not exceed that of cylinder oxygen, but the study was stopped because of a shortage of co­ balt. A studv was made by the

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Bureau of Mines in 1959 to find out how much it would cost to produce tonnage quantities of oxygen for the gasification of coal with oxygen carriers. The conclusion reached was that the process was not economical for the large quantities of oxygen required. However, BuMines is continuing to study alternate processes. More recently, oxygen carriers have been mentioned by Dr. Vaska as possible oxygen suppliers for space exploration. While the indium complex is unsuitable for these applications—in fact, it's not a good catalyst—Dr. Vaska says future work based on the How to spell proGreSs with only two letters knowledge of this simple system may uncover carriers which overcome pracWE'RE GROWING! Our recent merger with Palo Laboratory Supplies, Inc. has tical disadvantages. In addition, conmade GREINER SCIENTIFIC the largest laboratory supply source in the Greater tinued research in this field may lead New York area. That means greater selection . . . a more complete product to a better understanding of heteroline than ever before. Whatever your particular field may b e . . . clinical-medical, petroleum, research and development. . . Greiner's experience and expanded geneous catalysis and some biochemifacilities can serve your needs quickly and completely. The latest order cal reactions involving oxygen and hyprocessing techniques and equipment assure you faster, more efficient service. drogen, he points out. Greiner has more trucks, too, for speedier deliveries. Phone any time day or Past investigations on oxygen-carrynight: WO 6-4700 (area code 212). C^TiFTNF'T? ing properties of synthetic chelates are due in large part to Dr. Alelvin Calvin of the University of California, BerkeC O R P O R A T I O N ley, Dr. Harvey Diehl of Iowa State and PALO LABORATORY SUPPLIES, INC. University, Ames, and their associates. 22 N. MOORE ST., Dept. 523. NEW YORK 13, Ν . Χ Dr. Vaska's research on the indium complex indicates that activated complexes in homogeneous catalysis which cannot be directly observed may find stable models among synthetic coordination compounds of the third transition series. In addition, Dr. Vaska's A CLAIM work suggests that chemisorption of WORTH CHECKING hydrogen or oxygen on metal surfaces may be related to metal hydride and oxygen complexes, respectively. Oxygen Adduct. Elemental analysis, infrared spectra, monomelic molecular weight, nonelectrolytic character in solution, diamagnetism, electric moment, and reaction studies of the oxygen adduct [CUrCl ( CO ) ( Ph 3 P)o], suggest that the compound is a molecular peroxide of tervalent iridium [Science, 140, 809 (1963)]. Food Processing Both oxygen atoms are bonded to YOU'LL GET MORE WORK-LIFE FROM EACH PAIR OF the same central atom. In this proSURETY NATURAL RUBBER GLOVESposed structure, the orientation of oxyAND BETTER WORK FROM EACH EMPLOYE WHO WEARS THEM gen relative to the metal atom is Why more work-life? Surety's rubber chemists have developed their own analogous to that suggested by Dr. natural rubber compound for these general purpose gloves... and Surety's quality controls eliminate flaws and assure uniform thickness and strength. J. S. Griffith of the University of CamWhy better work from employes who wear them? Well, you can almost get the story just by picking one up (We'll send samples on request). bridge for oxyhemoglobin. Surety's exclusive Velvex finish means they always slip on and off easily. Assembling Small Parts Product assemblers prefer Suretys for the finger dexterity they allow. The oxygenation reaction is interThey're available in smooth or non-skid outer work surfaces, and in preted as an oxidation of the unistraight cuff or patented Turn-Cuff design. The distributor who handles Suretys in your area will help you select the style exactly suited valent (spin-paired d 8 ) and four-cofor each application. ordinate iridium compound to a tert ° i Ώ TÎ/ PROTECTION WITH SURETY FOR 36 YEARS valent (spin-paired d 6 ) and six-coorOVKt'VRUBBER COMPANY, Box 97-V-6,Carrollton,Ohio dinate iridium peroxo complex, Dr. EXPORT D I V I S I O N : 224 EAST 8th STREET · C I N C I N N A T I 2, O H I O General Industrial Application· I Vaska explains. JN CANADA: SAFETY SUPPLY CO., TORONTO

SCIENTIFIC

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Studies point to the hydrogen adduct being a molecular dihydride of lervalent iridium [H 2 IrCl(CO) (Ph 3 P)2]. The adduct is analogous to other stable metal hydride complexes obtained by conventional methods. The number and positions *of the iridium-hydrogen vibrational frequencies observed in the IR spectrum, together with the reversibility of hydrogénation, suggest that the two hydrogens occupy cis positions. The IR spectrum of the iridium dihydride also demonstrates an analogy with chemisorbed hydrogen on platinum, as reported by Dr. W. A. Pliskin and Dr. R. P. Eischens of the Texaco Research Center, Beacon, N.Y. The crystals of the starting complex [ I r C l ( C O ) ( P h 3 P ) 2 ] , do not react with either hydrogen or oxygen until dissolved in a nonpolar medium (the compound is insoluble in water). Most of the reactions were studied in benzene. The complex takes up one molecule of either oxygen or hydrogen for each atom of iridium. Both the oxygen and hydrogen adducts can be crystallized from solution. Crystals form when the complex stands in concentrated solutions under hydrogen or oxygen gas. Above 100° C , the crystals release hydrogen or oxygen. At room temperature, they are relatively stable. Photosensitive. The oxygen adduct is photosensitive, forming an intensely colored substance. To be seen clearly, this photocatalyzed reaction requires the presence of oxygen. Samples stored in the dark (in air) are unchanged after more than a year, Dr. Vaska says. When hydrogen or oxygen pressure above the solution is reduced, the adduct reverts to the starting material. This cycle may be repeated without affecting either the capacity or any other property of the carrier with hydrogen. However, repeated cycling of oxygenation-deoxygenation—about 13 cycles extending over 20 days in light—gives only about 70% recovery of the starting compound. Irreversible oxidation has been reported for all other oxygen carriers, but the nature of such reactions hasn't definitely been established, Dr. Vaska says. The rates of oxygenation for the iridium complex are considerably slower than those reported for all other oxygen carriers. The oxygenation-deoxygenation cycle rates are also slower than those found for the hydrogen system.

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