Alkaline earth metals compounds

For the most part it is true to say that the chemistry of the alkali and alkaline earth metal compounds is not that of the metal ion but rather that of the anion with which the ion is associated. Where appropriate, therefore, the chemistry of these compounds will be discussed in other sections, for example nitrates with Group V compounds, sulphates with Group VI compounds, and only a few compounds will be discussed here. 

The structure of the alkaline-earth metal compound CayC6o (for y < 5) follows the same space group Fm3m as for the heavy (M = K, Rb and Cs) alkali metal MxC6o compounds (x < 3) [27] and the Ca ions occupy both tetrahedral and octahedral sites. Because of the smaller size of the calcium ion, the octahedral sites can accommodate multiple Ca ions, and it is believed that up to three Ca ions can be accommodated in a single octahedral site [27]. Ba6C(jo and Sr6C60, in contrast, exhibit different crystal phases, such as the A15 and other bcc phases [28, 59],... 

Peterson and Scarrah 165) reported the transesterification of rapeseed oil by methanol in the presence of alkaline earth metal oxides and alkali metal carbonates at 333-336 K. They found that although MgO was not active for the transesterification reaction, CaO showed activity, which was enhanced by the addition of MgO. In contrast, Leclercq et al. 166) showed that the methanolysis of rapeseed oil could be carried out with MgO, although its activity depends strongly on the pretreatment temperature of this oxide. Thus, with MgO pre-treated at 823 K and a methanol to oil molar ratio of 75 at methanol reflux, a conversion of 37% with 97% selectivity to methyl esters was achieved after 1 h in a batch reactor. The authors 166) showed that the order of activity was Ba(OH)2 > MgO > NaCsX zeolite >MgAl mixed oxide. With the most active catalyst (Ba(OH)2), 81% oil conversion, with 97% selectivity to methyl esters after 1 h in a batch reactor was achieved. Gryglewicz 167) also showed that the transesterification of rapeseed oil with methanol could be catalyzed effectively by basic alkaline earth metal compounds such as calcium oxide, calcium methoxide, and barium hydroxide. Barium hydroxide was the most active catalyst, giving conversions of 75% after 30 min in a batch reactor. Calcium methoxide showed an intermediate activity, and CaO was the least active catalyst nevertheless, 95% conversion could be achieved after 2.5 h in a batch reactor. MgO and Ca(OH)2 showed no catalytic activity for rapeseed oil methanolysis. However, the transesterification reaction rate could be enhanced by the use of ultrasound as well as by introduction of an appropriate co-solvent such as THF to increase methanol solubility in the phase containing the rapeseed oil. 

By this approach, esters such as di(2-ethylhexyl) adipate and an oligomeric ester of neopentyl glycol have been synthesized recently by alcoholysis of dimethyl adipate ester and the corresponding alcohols, with alkaline earth metal compounds as the catalysts (171) (Scheme 30). These types of esters find application as lubricants, and it is suggested that they can be used as environment-friendly substitutes for petroleum-derived lubricants. The reactions were carried out with isooctane as a... 

As the carbon black structure may be reduced by the presence of alkali metal ions in the reaction zone [4.11], alkali metal salts, preferably aqueous solutions of potassium hydroxide or potassium chloride, are often added to the make oil in the oil injector. Alternatively, the additives may be sprayed separately into the combustion chamber. In special cases, other additives, e.g., alkaline-earth metal compounds which increase the specific surface area are introduced in a similar manner. 

Insertion of CSj in metal-hydride bonds gives metal dithioformates. Bonding of the ligands to the metal can take place in several ways (a) ionic in alkali and alkaline earth metal compounds (b) symmetric bidentate in most of the transition metal complexes and (c) as a positive symmetrically bonded ligand to (25), in which the HC(S)S has donated two electrons to the two electron-deficient dicarbanonaborane groups.36 Little is known about monothioformic acid and its complexes. 

Gryglewicz, S. Alkaline earth metal compounds as alcoholysis catalysts for ester oils synthesis, Appl. Catal., A, 2000, 192, 23-28. 

Alkali Metal and Alkaline-earth Metal Compounds... 

Compounds of the earth metals and alkaline earth metals Compounds of the heavy metals... 

Use of a support made of an alkaline earth metal compound [3 If]. Tribasic calcium phosphate, calcium carbonate, calcium fluoride, strontium titanate and magnesium aluminate are optimal supports. 

US patent 5,763,630 claims silver catalysts supported on other alkaline earth metal compounds than carbonates, such as calcium titanate, tribasic calcium phosphate, calcium molybdate, or calcium fluoride, as well as the magnesium and strontium analogues. Such supports provide significantly higher selectivity to the desired epoxide than would be expected from the performance of related materials. Selectivities are lower than those reported in the original Union Carbide patent. 

US patent 5,861,519 claims alkaline earth metal compound-supported silver catalysts containing tungsten and potassium promoters. 

In the present review, the principle causes of SCR catalyst deactivation are considered under five categories, and discussed in the order of (1) sulfur compounds, (2) alkali metal and alkaline earth metal compounds, (3) arsenic and other heavy metal compounds, (4) fouling or masking by deposits, with pore blocking or surface coating, and (5) thermal degradation. 

In the row of corresponding alkaline-earth metal compounds, only the sulfides of strontium and barium and analogs with europium are known. Because the number of cations incorporated in the structure halves, the charge being doubled as a result, a linkage which is as compact as possible is favored this corresponds to the formula A2Re68ii = A2 [Rc688]86/2 where A = Ba, 8r or Eu. ... 

Alkali Metal and Alkaline Earth Metal Compounds. 146... 

Iron, M.A., Oren, M., Martin, J.M.L. Alkali and alkaline earth metal compounds core-valence basis sets and importance of subvalence correlation. Mol. Phys. 2003,101,1345. 

Sorbents based on alkali or alkaline earth metal compounds are recommended for high-temperature capture of hydrogen chloride (and halides in general). However, metal vapours can form from these metallic compounds at high temperatures, with danger of condensation during fuel gas utilization. 

In examining metallic compounds that serve as supports for Pt and Pd catalysts, the metals and metallic compounds as catalyst support are only limited to a few elements. This is because some metals, such as lead, mercury, cadmium, bismuth, tin, zinc, copper and iron have a toxic effect on the catalyst, whereas light metals and alkaline earth metal compounds are without toxic for catalyst, and they can in some cases enhance the selectivity and activity of the catalysts. 

The only alkaline earth metal compounds known are bis(triorganosilyl)magnesium complexes with a solvent. 

The development of the heavy alkaline-earth metal bis(bis(trimethylsilyl)amides, M[N(SiMe3)2]2(thf)2, has been instrumental in the use of the transaminadOTi route as a viable and dependable synthetic route towards the preparadmi of alkaline-earth metal compounds. The amides, M[N(SiMe3)2]2(thf)2, can be prepared via salt metathesis involving treatment of the metal halides with alkali metal amide (Ca-Ba) [182, 183]. The heavier metal (Sr, Ba) amides can also be obtained by direct metallation in liquid, anhydrous ammonia (Sr and Ba) [83,90,91, 184-187]. 

Westerhausen M, Gartner M, Fischer R, Langer J, Yu L, Reiher M (2007) Heavy Grignard reagents challenges and possibilities of aryl alkaline earth metal compounds. Chem Eur J 13 6292-6306... 

The aldol reaction is an important carbon-carbon bond-forming method for constructing p-hydroxy carbonyl compounds in which new stereogenic centers are created. Especially, regio- and stereoselective aldol reactions are the most useful for organic synthesis of complex molecular skeletons [11-15]. From a viewpoint of atom economy, an aldol reaction via direct formation of an enolate with a catalytic amoimt of base is highly desired, and high Brpnsted basicity of the alkaline-earth metal compounds is suitable for this purpose. In recent researches on chiral alkaline-earth metal catalysis, direct-type asymmetric aldol and related reactions have been developed. 

---