Methanolic metal precursors

Imidazolidinium salts can also be transformed into the corresponding diamino ortho-esters by alkaline alkoxylate, and upon alcohol elimination at elevated temperature the imidazolidin-2-ylidenes can be trapped. The reaction of tria-zolium salts with sodium methanolate in methanol yields 5-methoxy-4,5-dihydro-IH-triazole which also eliminates methanol upon heating in vacuo. The resulting triazolin-5-ylidenes can either be isolated or trapped by an appropriate metal precursor [Eq. (19)]. Benzimidazolin-2-ylidenes are similarly accessible by this route. 

Either protic (alcohols, preferentially methanol) or aprotic solvents (toluene, dichloromethane, THE) can be used, depending on the structure of the metal precursors that can generate the catalysts by a number of pathways. Metals other than palladium, for example nickel [4], can form active catalysts for alkene/CO copolymerisation, yet with largely lower productivities as compared to structurally similar palladium precursors [1]. For this reason, only Pd"-catalysed alkene/CO copolymerisation reactions are reviewed and commented in the present chapter. 

One-dimensional coordination polymers of copper, zinc and silver have also been prepared using solvent free techniques (Figure 2.4). This was achieved by grinding the ligand (DABCO or trans-1,4-diaminocyclohexane) with the metal precursor for 5 min, followed by recrystallization in water-methanol. No yields are reported for many of these reactions because of the small scale on which they were conducted. However, in some cases, different structures are reported when the reaction is conducted in solution compared with the solid state. 

Toyira, J., P. Ramirez de la Piscinal, J. L. G. Fierrob, and N. Homs, Catalytic performance for CO2 conversion to methanol of gallium-promoted copper-based catalysts influence of metallic precursors , Appl. Catal. B Environ., vol 34, Issue 4, 28 November 2001, pp 255-66. 

Toyir, J. Piscina, PR. Fierro, J. L. G. Homs, N. Catalytic Performance for CO Conversion to Methanol of Gallium-Promoted Copper-based Catalysts Influence of Metallic Precursors. Appl Catal, B. 2001, 34,255-266. 

Besides supported (transition) metal catalysts, structure sensitivity can also be observed with bare (oxidic) support materials, too. In 2003, Hinrichsen et al. [39] investigated methanol synthesis at 30 bar and 300 °C over differently prepared zinc oxides, namely by precipitation, coprecipitation with alumina, and thermolysis of zinc siloxide precursor. Particle sizes, as determined by N2 physisorpt-ion and XRD, varied from 261 nm for a commercial material to 7.0 nm for the thermolytically obtained material. Plotting the areal rates against BET surface areas (Figure 3) reveals enhanced activity for the low surface area zinc... 

Et4N]2[Fe2lr2(CO)i2] cluster precursor, which exhibit a high activity in the synthesis of methanol from CO and H2, were studied by Ir and Fe Mossbauer spectroscopy. The study extends from the precursors via the fresh to the aged catalysts. The presence of iridium in the metallic state as well as the presence of trivalent, divalent and alloyed iron is detected. Representative Ir and Fe Mossbauer spectra are shown in Fig. 7.69. Information about the adsorption on the surface of MgO... 

For the preparation of CoSalophen Y the Co—Y was impregnated by salicy-laldehyde, and 1,2-phenylenediamine in methanol was added slowly to the mixture.107 This was a successful encapsulation of a salen-type complex with larger diamine than the ethylenediamine, a successful preparation of an encaged metal-salen complex by the intrazeolite ligand synthesis method, and a successful intrazeolite synthesis using two different precursor molecules. 

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