Monodentate carbonate species

The lower stability is due to the lower crystal field stabilization on passing from coordination 5 to 6 than from 4 to 5. Finally, the monodentate carbonate species (bands at 1490 and 1365 cm"1) may be formed on sites with the Cr3+ ion having coordination number 5 (only one anion vacancy) ... 

Figure 1 shows FT-IR spectra of reduced Ni/ZSl and KNiCa/ZSI catalysts before and after CO2 adsorption, and under the C02-reforming conditions. The behavior of adsorbed CO2 on KNiCa/ZSl was different from that on Ni/ZSI. FT-IR spectrum of KNiCa/ZSI even after reduction at 700 °C showed two evident bands at 1480 and 1410 cm which did not appear that on Ni/ZSI catalyst. These bands could be assigned to mainly asymmetric (Vas(OCO)) and symmetric stretching vibration (vs(OCO)) modes of monodentate carbonate species coordinated to Ca oxide or K oxide of the catalyst, respectively [3]. The intensities of these... 

Haider et al. used ATR-IR with MBS to study the surface properties of Mg-Al and Cu-Mg-A1 mixed metal oxide supports for gold nanoparticles with various metal ratios. In previous work the group had found that Cu increased the activity of Au deposited on metal oxide supports for alcohol oxidation. CO2 was used to probe the various surfaces as C02-saturated toluene and N2-saturated toluene were cycled in the MES experiments. As opposed to conventional ATR-IR experiments, the addition of MES improved the spectral resolution and made it possible to distinctly identify bidentate and monodentate carbonate sirrface species. It was found that Mg- and Al-rich oxides formed bidentate species while Cu-rich metal oxide supports formed a mix of bidentate and monodentate carbonate species. 

Reaction of [Ir(cod)Cl]2 with (6-methyl-2-pyridyl)methyl lithium yields the binuclear species [(cod)Ir(/i-CH2-py-6-Me-C, /V)]2, (401). The Ir centers in (401) are 3.5889(3) A apart, indicating little metal-metal interaction. Treatment of (401) with PPh2Et yields [(cod)Ir(PPh2Et)2(CH2-py-6Me)], which contains the monodentate, carbon-bound pyridylmethyl ligand. 

Ito and co-workers observed the formation of zinc bound alkyl carbonates on reaction of carbon dioxide with tetraaza macrocycle zinc complexes in alcohol solvents.456 This reversible reaction was studied by NMR and IR, and proceeds by initial attack of a metal-bound alkoxide species. The metal-bound alkyl carbonate species can be converted into dialkyl carbonate. Spectroscopic studies suggested that some complexes showed monodentate alkyl carbonates, and varying the macrocycle gave a bidentate or bridging carbonate. Darensbourg isolated arylcarbonate compounds from zinc alkoxides as a by-product from work on polycarbonate formation catalysis.343... 

CO2 and SO2 are frequently considered as acidic species. The adsorption of the former on MgO has been used to classify MgO as basic surface. The adsorption on 0 leads to C03 and SO3"" species that are nicely evoked to prepare the adsorbed species toward reactivity. For CO2, this leads to monodentate or bidentate carbonates and to hydrogen carbonates (bicarbonates). Monodentate carbonates have been postulated together with vertical C02[l]. On MgO[25] and Ti02 surfaces[26] the... 

Carbon dioxide is a hard acid, and as such, it is expected to initially adsorb on hard base sites, presumably oxygen anions and surface hydroxyl groups. However, the adsorbed carbon dioxide can be as carboxylate or carbonate species, and the carbonate may be monodentate or bidentate ... 

Methylation of the dihaptothioacyl complex 22 affords compound 23 containing a bidentate carbene ligand, which on reaction with chloride ion leads to the neutral monodentate carbene complex 24 (50,51). The chelate carbene complex 26 is generated in a novel interligand reaction from the thiocarboxamidothiocarbonyl cation 25. The thiocarbonyl carbon acts as the electrophilic component in this reaction, and 26 is further alkylated to a bidentate dicarbene species (52). 

The use of bulky monodentate m-terphenyl ligands in the stabilisation of d-block organometallic compounds is surveyed. Importantly, these ligands have facilitated the isolation of hitherto unknown species containing low-coordinate centres and metal-metal multiple bonds. This review reports on these advances with emphasis on the synthesis, structural characterisation and, where possible, reactivity studies of complexes featuring metal-carbon bonds between m-terphenyl ligands and the transition metals. 

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