Metal acetate hydrazines

Metal acetate hydrazines M(CH3COO)2(N2H4)2 (M = Mn, Co, Ni, Zn, and Cd) are synthesized by the reaction of freshly prepared metal acetate hydrates with excess hydrazine hydrate [11]. The reaction is instantaneous and yields hydrazine complexes as shown by (3.7) ... 

The features of the thermal analysis data show that metal acetate hydrazines decompose exothermically, in three steps, to their respective metal oxides. Manganese, cobalt, zinc, and cadmium complexes decompose through the formation of their corresponding metal acetates, while the nickel complex decomposes through a mixture of nickel metal and nickel acetate (Figure 3.5). The zinc complex however, loses both hydrazine molecules in a single step, while Mn, Co, and Cd complexes lose hydrazine in two steps. The metal oxide formation temperatures from the decomposition of metal acetate hydrazine complexes occur at 275-385 °C. These are lower than those reported for metal acetate hydrates, which occur at 350-400 °C. 

The procedure for synthesizing mixed metal acetate hydrazines is to add an excess of alcoholic hydrazine hydrate to a solution containing a mixture of the corresponding metal acetates, in the molar ratio of 1 2 [12]. The precipitated complexes are filtered, washed with ethanol and then diethyl ether, and stored in a vacuum desiccator over P2O5. This method has been used to prepare solid solutions of mixed metal acetate hydrazines of the type Mv3Co2/j(CH3COO)2(N2H4)2 (M = Ni " " or Zn ), which are precursors to nickel and zinc cobaltites. 

As the structure of metal acetate hydrazine complexes appears to be isomorphous, the formation of mixed metal hydrazines takes place easily. This is further confirmed by the identical infrared spectra of Nii/3Co2/3(CH3COO)2(N2H4)2 with the nickel and cobalt acetate hydrazine complexes (Figure 3.6). 

These precursors decompose exothermically in the temperature range 165-345 °C to yield the corresponding cobaltites, as depicted by the thermal analyses (Figure 3.7) [13]. Table 3.9 gives the thermal data of the mixed metal acetate hydrazines. 

Mahesh, G.V. and Patil, K.C. (1986) Thermal reactivity of metal acetate hydrazinates. Thermochimica Acta, 99, 153-158. 

The formation of cobaltites (MC02O4) from the combustion of mixed metal oxalate/acetate hydrazine complexes and solid solutions of hydra-zinium metal hydrazine carboxylate hydrates have been discussed in Chapters 3 and 4, respectively (Sections 3.2.4.1, 3.2.6 and 4.6). The final product, confirmed by X-ray diffraction pattern, shows the characteristics of cobaltite spinels. Similar to cobaltites, mixed metal oxalate/acetate hydrazines complexes undergo single-step decomposition to form... 

This is the reason why, for example, the zero order formic acid dehydrogenation may easily be measured on bulk metal catalysts at 200-300°C. whereas the approximately first order ethanol dehydrogenation requires highly activated porous metals of large specific surface in order to become measurable under the same conditions. The same has been shown for the decomposition of formaldehyde, acetic acid, and hydrazine hydrate. In these cases, the fractional surface coverage is simply 1000 times lower than in the case of a zero order reaction. 

The earliest of these studies was on PbS. PbS can have either p- or n-type conductivity, although CD PbS is usually p-type. Based on the belief that the p-type conductivity may be due to alkali metal cations from the deposition solution, an alkali metal—free deposition, using lead acetate, thiourea, and hydrazine hydrate was used [33]. While initially n-type, the film converted to p-type in air. Attempts to stabilize the p-type material by adding trivalent cations to the deposition solution were unsuccessful. However, deposition of the PbS on a trivalent metal, such as Al, did stabilize the n-PbS, at least for a time. In this way, p-n junctions were made (the PbS close to the trivalent metal was n-type, while the rest of the film was p-type). Photovoltages up to 100 mV were obtained from these junctions at room temperature and almost 300 mV at low temperatures (90 K). 

Methods (i) and (ii) require palladium(II) salts as reactants. Either palladium acetate, palladium chloride or lithium tetrachloropalladate(II) usually are used. These salts may also be used as catalysts in method (iii) but need to be reduced in situ to become active. The reduction usually occurs spontaneously in reactions carried out at 100 °C but may be slow or inefficient at lower temperatures. In these cases, zero valent complexes such as bis(dibenzylideneacetone)palladium(0) or tetrakis(triphenylphos-phine)palladium(O) may be used, or a reducing agent such as sodium borohydride, formic acid or hydrazine may be added to reaction mixtures containing palladium(II) salts to initiate the reactions. Triarylphosphines are usually added to the palladium catalysts in method (iii), but not in methods (i) or (ii). Normally, 2 equiv. of triphenylphosphine, or better, tri-o-tolylphosphine, are added per mol of the palladium compound. Larger amounts may be necessary in reactions where palladium metal tends to precipitate prematurely from the reaction mixtures. Large concentrations of phosphines are to be avoided, however, since they usually inhibit the reactions. 

A solution of perfluoroalkyl iodide (0.4 mmol), a-chlorostyrene (1.2 mmol) and Bu3SnSnBu3 (0.44 mmol) in benzene (3 ml) was irradiated using a metal halide lamp (National Sky-beam MT-70) in Pyrex tube under 02 atmosphere for 5 h. After removal of the solvent, ethanol and hydrazine acetate were added. The resultant solution was stirred under refluxing conditions for 2 h. After removal of the solvent, the residue was chromatographed on silica gel using a mixture of hexane and dichloromethane as an eluent, to give perfluoroalkylated pyrazole in 59% yield [117]. 

Many heterocyclic bases can be oxidized to A-oxides with sodium perborate and acetic acid in the absence of metal catalysts.352 Use of a smaller excess of oxidant leads to diazo compounds.353 Aliphatic amines can be converted to nitroso products. Sodium perborate/acetic acid systems can also cleave hydra-zones, regenerating carbonyl compounds which have been protected by hydrazine formation.354... 

Usually decarboxylation is accomplished by heating the acids above their melting points, often in the presence of a copper-chromium catalyst. Imidazole-4,5-dicarboxylic acid can be monodecarboxylated by heating its monoanilide imidazole- and benzimidazole-2-carboxylic acids decarboxylate very readily indeed, so readily that the carboxyl function makes a useful blocking group in metallation procedures (see Scheme 7.2.1) [3-5]. A potentially useful method of preparation of imidazole-4-carboxylic acid derivatives heats the 4,5-dicarboxylic acid (2) with acetic anhydride to form (1), which is essentially an azolide and very prone to nucleophilic attack which cleaves the nitrogen-carbonyl bond (Scheme 8.3.1). With methanol the methyl ester (3) is formed with hydrazines the 4-hydrazides (4) result [6]. 

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