Carbon monoxide interactions with

An interesting oxycarbonyl cluster has been isolated in the reaction of 0s04 with CO under pressure. This was an intermediate in the preparation of the Os3(CO)i2. The X-ray analysis has established this as a cubane structure, with an oxygen bridging the four faces of the osmium tetrahedron. The Os-Os distance is 3.20 A and implies no bonding between the osmium centers. This molecule is of obvious interest as a potential model in the studies of carbon monoxide interaction with metal oxides and also metal surfaces, when the formation of metal oxides occurs (200). 

The rates of production of the heat evolved when a dose of carbon monoxide interacts with NiO(250) containing either 0 (ads) ions (Reaction 4) or C(V(ads) ions (Reaction 2) are given as a function of time in Figure 6. In both cases, the same amount of carbon monoxide has been introduced previously to this particular dose. Thermochemical cycles and direct observation of the presence of carbon dioxide in the cold trap confirm that, during the interaction of this particular dose of CO, carbon dioxide is desorbed to the gas phase. 

Study of Hydrogen and Carbon Monoxide Interactions with PaUadium-Y Zeolite by ESR and IR Spectroscopy... 

These transformations share common initial steps in which the carbon monoxide interacts with the trialkylborane to give an intermediate organoborate. This readily transfers one of its alkyl groups to the carbon atom derived from carbon monoxide to give intermediate X (Figure B3.1). 

Such a mechanism of carbon monoxide interaction with active centers is compatible with the data on the slow copolymerization of CO with ethylene found for the ethylene polymerization by some one-component catalysts This copolymerization may proceed also in the case of two-component catalysts resulting in an increase of the number of radioactive tags in the polymer with time (see Fig. 1). Arguments have been given that the rapid increase of polymer radioactivity in the initial period (5-10 min) is due to the insertion of the first CO molecule into the active metal-carbon bond. 

Most of the gas adsorbed at room temperature ( 99%) is desorbed, either at room temperature or at higher temperatures as carbon monoxide. The possibility of an interaction between carbon monoxide and cationic or anionic sites without formation of desorbable carbon dioxide must be therefore envisaged. Infrared measurements have shown, indeed, that carbon monoxide interacts with both types of sites (60). 

The same sequence of adsorptions (O2-CO) was also studied on the surface of NiO(250°) [41). As in the case of NiO(200°), adsorption of carbon monoxide on the sample containing preadsorbed oxygen (1.90 cm /gm) (Table II) changes the color of the sample from black to green and decreases its electrical conductivity (1.8 x 10- ohm-i cm- ) to the low initial value. However, this time, carbon dioxide is found in the cold trap placed near the sample. Calorimetric results reported in Table II indicate also that carbon monoxide interacts with preadsorbed oxygen since the heats of adsorption of carbon monoxide are higher on the black sample (Table II) than on the pure surface of NiO(250°) (Fig. 12). 

Infrared spectroscopic studies have shown that adsorbed carbon monoxide interacts with Brensted acid Si(OH)Al groups of the zeolite H-ZSM-5 forming hydrogen-bonded H-CO and H—OC species, which are characterized by C-0 stretching IR absorption bands at 2175 and 2112 cm", respectively. By means of variable-temperature FTIR spectroscopy, these C-bonded and O-bonded adducts were found to be in a temperature dependent equilibrium which can be described as ZH CO = ZH- OC, where Z stands for the zeolite framework. The corresponding enthalpy change was found to be AH° = 4.2 kJ mol", as derived from a van t Hoff analysis of the intensity of the corresponding IR absorption bands as a function of temperature. 

The present paper focuses on the interactions between iron and titania for samples prepared via the thermal decomposition of iron pentacarbonyl. (The results of ammonia synthesis studies over these samples have been reported elsewhere (4).) Since it has been reported that standard impregnation techniques cannot be used to prepare highly dispersed iron on titania (4), the use of iron carbonyl decomposition provides a potentially important catalyst preparation route. Studies of the decomposition process as a function of temperature are pertinent to the genesis of such Fe/Ti02 catalysts. For example, these studies are necessary to determine the state and dispersion of iron after the various activation or pretreatment steps. Moreover, such studies are required to understand the catalytic and adsorptive properties of these materials after partial decomposition, complete decarbonylation or hydrogen reduction. In short, Mossbauer spectroscopy was used in this study to monitor the state of iron in catalysts prepared by the decomposition of iron carbonyl. Complementary information about the amount of carbon monoxide associated with iron was provided by volumetric measurements. 

Spencer and Schaumburg 2000). Although the primary reaction of carbon monoxide is with hemoglobin, it also interacts with myoglobin, cytochromes, and metalloenzymes (e.g., cytochrome c oxidase and cytochrome P450) (WHO 1999). The health importance of these secondary reactions is not well understood. 

Organic ligands in which no protons are attached to the carbon atoms interacting with the metal may be investigated, e.g., 7r-bonded al-kynes or substituted olefins, complexes formed by carbon monoxide or substituted carbenes. 

Carbon monoxide reacts with [Fe(TPP)] to form a five-coordinate complex [Fe(TPP)CO], which can be reduced electrochemically to the corresponding iron(I) species from which, however,245 CO spontaneously dissociates. The Fe—CO interaction is stabilized by the,presence of hydrocarbon chains bound by amide linkages to the ortho position of the TPP phenyl rings. Carbon monoxide adducts of iron(I) complexes of a number of these superstructured porphyrins have been reported.245 The chemistry of these highly reduced species is of relevance to understanding240 the reactions of cytochrome P-450 and the peroxidases. 

Isocyanates can be prepared from azides by reaction with carbon monoxide. The reaction has been at first reported to proceed only with catalysis of rhodium or iridium carbonyl complexes . Later work has however shown that aryl azides and carbon monoxide interact without catalysis at temperatures of 160-180° and pressures of 200-300 atm, yielding aryl isocyanates (86) in good yields. Ethyl azidoformate yielded under these conditions ethoxyisocyanate . 

Interaction (7c) between adsorbed species is the slowest step of the reaction mechanism (72). Calorimetric experiments have confirmed indeed that the heat is released more rapidly during interactions (5a) and (6) than when carbon monoxide reacts with C03"(ads) ions [interaction (7)]. The following calorimetric experiment (75) has shown, moreover, that C03-(ads) ions may be formed on the surface of NiO(200°)... 

While stable binary actinide carbonyls are still unknown, research in this area focused mainly on the detection and theoretical investigation of unstable molecules such as the monocarbonyl complexes of thorium and uranium. The possible molecular structures U-GO, U-OG, and GUO of carbon monoxide interacting on a uranium metal surface have been studied by density functional theory (DFT).14 GUO has been produced experimentally by reaction of laser-ablated U atoms with CO in excess argon and trapped in a triplet state in solid argon at 7 K.15 Studies of the reaction of thorium atoms with CO have been carried out. The reaction of laser-ablated thorium atoms with carbon monoxide in excess neon gave the first thorium carbonyl complex, Th-GO, which rearranges photochemically to CThO (Scheme l).16... 

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