CO binding

Next, (1) CO binds to Cluster C to yield a Credi-CO complex (2) CO undergoes attack by the metal-bound hydroxide and is oxidized to CO2 as Cluster C is reduced by two electrons to the Cred2 state (3) CO2 is released and a second CO molecule binds to Cluster C to form a Cred2-CO complex (4) electrons are transferred from Cred2-CO to reduce Cluster B as the second molecule of CO2 is released. This mecha-... 

Unzai S et al Rate constants for O2 and CO binding to the alpha and beta subunits within the R and T states of human hemoglobin. J Biol Chem 1998 273 23150. 

Figure 5.10. Defects consisting of oxygen vacancies constitute adsorption sites on a Ti02 (110) surface. Note how CO binds with its lone-pair electrons on a Ti ion (a Lewis acid site). O2 dissociating on a defect furnishes an O atom that locally repairs the defect. CO2 may adsorb by coordinating to an O atom, thus forming a carbonate group. [Figure adapted from W. Gopel, C. Rocher and R. Feierabend, Phys. Rev. B 28 (1983) 3427.]...

The presence of impurities is an important issue in mobile applications where the hydrogen at least initially will be supplied by the decomposition of hydrocarbons or methanol in on-board reformer systems as long as no appropriate hydrogen storage media are available. In such systems CO is an unavoidable by-product, and since CO binds more strongly to Pt than hydrogen, the low operating temperature... 

McMahon, M. T., deDios, A. D, Godbout, N., Salzmann, R., Laws, D. D., Le, H., Havlin, R. H., Oldfield, E., 1998, An Experimental and Quantum Chemical Investigation of CO Binding to Heme Proteins and Model Systems A Unified Model Based on 13C, 170 and 57Fe Nuclear Magnetic Resonance and 57Fe Mossbauer and Infrared Spectroscopies , J. Am. Chem. Soc., 120, 4784. 

Nickel-selenium coordination compounds have received attention in recent years, because a unique Ni-selenocysteine interaction was revealed in the active site of [FeNiSe]-hydrogenases.1083,1084 Of particular interest in this regard are mixed CO/selenolate complexes. Distorted square planar (393) was prepared from [CpNi(CO)]2, PhSeSePh, and [Fe(CO)3(SePh)3] and provides the first example of CO bound to a square planar Ni11 center in thiolate/selenolate environment.1085,1086 Upon addition of RSSR, species of the series [Ni(CO)(SR) (SePh)3 ] are formed. //(CO) ranges from 2,023 cm-1 to 2,043 cm-1 and is regarded as a spectroscopic reference for the CO binding site in [NiFeSe] hydrogenases. 

Ni(terpy)(1001)2] is reduced by aqueous dithionate to a Ni1 complex, which displays reversible CO binding, and also reacts with H-.2401... 

Table 4.24. Bond lengths Rwc, angles 6Cwc, and incremental CO binding energies A/ (+CO) for a and cu bonds o/W(CO) complexes (see Fig. 4.36)...

Figure 4.103 Incremental CO binding energies, Eq. (4.129), for M(CO) complexes of group 6 metals Cr (circles), Mo (squares), and W (triangles). For n = 3, the quantity plotted is the average energy of dissociating all three carbonyls from M(CO)3.

The surface composition and the availability of certain adsorption sites are not the only factors that determine how CO binds to the surface. Interactions between CO and coadsorbed molecules play an important part as well. A RAIRS study by Raval... 

Figure 9.14 Thermal desorption spectra of CO from clean (left) and potassium-promoted Ni (110) (middle and right) mea-sured at a heating rate of 13 K/s. The spectra exhibit two desorption states for CO on promoted surfaces and indicate that CO binds more strongly to sites adjacent to potassium (from Whitman and Desorption Temperature (K) Ho [46]).

Subsequent experiments on the same system aimed to determine the stability of the isocyanate species and to measure the reactivity of the Pd(lll) model catalyst for the CO + NO reaction.125 When exposing the sample to different CO/NO ratios (2 and 1.5) at room temperature, peaks were obtained which corresponded to threefold NO, atop NO, and threefold CO, with the higher CO/NO ratio leading to a greater amount of CO binding. When the samples were flashed to 650 K and cooled back to 300 K in the presence of the reaction mixtures, isocyanate was formed. However, as is apparent from Figure 10.25, an increase in the CO/NO ratio strongly favored isocyanate formation. 

Figure 9.17 Measurements of CO spectra before and after incubation with MBI. (a) CO measurement indicating partial loss of CO binding despite being an apoprotein adduct (b) positive heme adduct, ABT, showing heme alkylation and subsequent disruption of CO binding and (c) MBI, midazolam thought to result from apoprotein adduct also showing marginal loss of CO binding [198].

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