Nitrito species

A careful investigation of this feature suggests that it is attributable to N02 associated with both Bronsted acid and M+ cations [29]. The doublet at 1400 cm is identical in position and appearance to that observed in a sample of Na-Y doped with NaNOs [30]. We therefore assign this peak to a NO3- species affiliated with the residual sodium in the catalyst. The position of the band at 1528 cm- is very similar to that for nitrito species in Co-A and Co-Y [22, 23] and is, therefore, assigned to Co-ONO. The features at 1599, and 1574 cm- are best assigned to C0-O2NO [30]. The band at 1633 cm- is similar to that observed on H-, Na-, and Cu-ZSM-5. We believe that this feature is best assigned to nitrito (NO2) or nitrate (NO3-) species. 

Since the formation of NO2 can occur homogeneously, it was of interest to establish whether adsorbed NO could be oxidized. NO was adsorbed at 225 C, after which the infrared cell was purged with He and subsequently a stream of 10.1% O2 in He was allowed to flow over the catalyst. Prior to the introduction of the 02-containing stream, the only features evident were those for mono- and dinitrosyls. In the presence of O2 at 225 °C, the intensities of the bands for both mono- and dinitrosyl species attenuated and new features appeared at 1628 and 1518 cm-, corresponding to nitrate and nitrito species, respectively. A similar experiment carried out in the absence of O2, showed only a small decrease in the intensity of the nitrosyl bands due to NO desorption and the absence of bands for nitrate and nitrito species during a 30 min purge in He at 225 °C. 

The reaction between methane and NO in the presence of 02 over manganese-exchanged zeolite Mn-ZSM-5 [62a] begins with the adsorption of O2 followed by NO to form a nitrito species ... 

Absorbed nitrito species are then available to react with methane, forming adsorbed CH3NO species with the release of hydroxyl radicals ... 

One example was reported by Tolman and coworkers (78) who found that the copper(I) complex C Tp112 (TpR2=tris(3-(R2)-5-methylpyrazol-l-yl)hydroborate) promotes NO disproportionation via a weakly bound CuITpR2(NO) intermediate (formally a MNO 11 species). The products are N20 and a copper(II) nitrito complex (Eq. (36)). The rate law established the reaction to be first-order in copper complex concentration and second-order in [NO], and this was interpreted in terms of establishment of a pre-equilibrium between NO and the Cu(I) precursor and the Cux(NO) adduct, followed by rate-limiting electrophilic attack of a second NO molecule (mechanism B of Scheme 5) (78b). 

Sometimes a formal disproportionation of NO occurs. For example reaction with Co(NO)(PPh3)3 yields the nitrito dinitrosyl species Co(N02)(NO)2(PPh3) and nitrogen gas is evolved.82 The initial step in this reaction may be described as in equation (7). 

In plant solutions, up to 70% of the Ru(NO) 3+ may be in the form of inextractable nitrito complexes.305 However, as the nitrato species extract the mass action affect of the nitrate present may lead to the substitution of nitrite with nitrate, even though the former gives the more... 

Payen and coworkers (Le Bourdon et al., 2003) investigated Pd/y-A1203 catalysts under DeNO reaction conditions with Raman and IR spectroscopy. Their instrument allows the quasi-simultaneous recording of both IR and Raman spectra. Several adsorbed NO species were identified (ranging from nitrates, nitrito, nitrate, and nitro species) by exploiting the high sensitivity of IR spectroscopy for adsorbate vibrations and the specificity of Raman spectroscopy for the vibrations of catalyst— adsorbate bonds. 

The long relaxation time of this system (10 h) allows in situ characterization of the elusive cis isomer by spectral techniques. Long-term photolysis of this mixture leads to the formation of the known dinuclear species (n-PrjP)jPd2Cl. Quantitative photosolvolysis of a complex of the sterically bulky ligand 4-methyl-1,1,7,7-tetra-ethyldiethylenetriamine, (MeEt dien) shows the nitro complex to undergo linkage photoisomerization to the nitrito isomer followed by replacement of the coordinated nitrite by solvent ... 

PdL2L ] adducts are formed by reaction of [PdL4] with small molecules such as NO, SO2, CS2, or O2. [PdL2(02)] species have shown to be active oxidizing agents reacting with CO2, SO2, NO2, or NO to yield carbonato, sulfato, nitrato, and nitrito complexes respectively (equation 5). ... 

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