Metal aluminum halides

Chlorine or bromine react with benzene in the presence of carriers, such as ferric halides, aluminum halides, or transition metal halides, to give substitution products such as chlorobenzene or bromobenzene [108-86-17, C H Br occasionally para-disubstitution products are formed. Chlorobenzene [108-90-7] ... 

An efficient catalyst for thermal isomenzations of halofluorocarbons [6, 7, 8, 9] IS prepared by treatment of alumina with dichlorodifluoromethane at 200-300 °C [9] or aluminum chloride with chlorofluorocarbons in the presence of metals [W] or palladium on alumina [II These catalysts are far more efficient than aluminum halides themselves (equations 1 and 2)... 

Thermolysis rates are enhanced substantially by the presence of certain Lewis acids (e.g. boron and aluminum halides), and transition metal salts (e.g. Cu ", Ag1).46 There is also evidence that complexes formed between azo-compounds and Lewis acids (e.g. ethyl aluminum scsquichloridc) undergo thermolysis or photolysis to give complexed radicals which have different specificity to uncomplexed radicals.81 83... 

To optimize the alkylation conditions, ferrocene was reacted with allyldimethyl-chlorosilane (2) in the presence of various Lewis acids such as aluminum halides and Group lO metal chlorides. Saturated hydrocarbons and polychloromethanes such as hexane and methylene chloride or chloroform were used as solvents because of the stability of the compounds in the Lewis acid catalyzed Friedel-Crafts reactions. The results obtained from various reaction conditions are summarized in Table IV. 

But first the synthesis had to come John was interested in reduced metal halides, particularly for the post-transition metals cadmium, galHum, and bismuth (his Ph.D. dissertation was on anhydrous aluminum halides and mixed halide intermediates, a good start for what was to come ). However, he was not yet actively interested in rare-earth metals and their remarkable solubility in their halides. But these elements lured him one floor below where Adrian Daane headed the metallurgy section of Spedding s empire. He knew how to produce rare-earth metals with high purity and in sufficient quantity and also how to handle tantalum containers. What if one gave it a tr/ and reduced some rare-earth metal halides (John insists that this term is used correctly) from their respective metals at high temperatures under appropriate conditions. 

Co. In the presence of cobalt(II) chloride and metallic aluminum, allylic halides react with aldehydes at room temperature in tetrahydro-furan-water to afford the corresponding alcohols in high yields.174... 

Halomet [Halogen metal] A process for reducing halides to metals by reaction with metallic aluminum or magnesium in a closed vessel. Invented in 1968 by R. Nowak and W. Schuster at Halomet, Basle. 

The experimental evidence which has accumulated in recent years shows that in every system which has been rigorously investigated the polymerization of olefins by metal halides depends upon the presence of some third substance, the co-catalyst [2-8]. The function of the cocatalyst is to provide the ions which start the polymerization proper, by forming an ionogenic complex with the metal halide. In most systems the metal halide is not consumed in the course of the reaction, so that the term catalyst in its classical sense may be retained in this respect. Exceptions to this are some polymerizations involving aluminum halides in the polymerization of propene [9], and possibly of styrene and a-methyl styrene [10], these catalysts may be inactivated by the formation of stable complexes. In other cases, such as the... 

Silica is reduced to silicon at 1300—1400°C by hydrogen, carbon, and a variety of metallic elements. Gaseous silicon monoxide is also formed. At pressures of >40 MPa (400 atm), in the presence of aluminum and aluminum halides, silica can be converted to silane in high yields by reaction with hydrogen (15). Silicon itself is not hydrogenated under these conditions. The formation of silicon by reduction of silica with carbon is important in the technical preparation of the element and its alloys and in the preparation of silicon carbide in the electric furnace. Reduction with lithium and sodium occurs at 200—250°C, with the formation of metal oxide and silicate. At 800—900°C, silica is reduced by calcium, magnesium, and aluminum. Other metals reported to reduce silica to the element include manganese, iron, niobium, uranium, lanthanum, cerium, and neodymium (16). 

Its molecular structure (Figure 37) consists of a centrosymmetric dimer with a bridging H2Al(OR)( U-OR)2Al(OR)H2 entity. The Ta atoms are approximately square pyramidal, with the four phosphorus atoms forming the basal plane (Ta lies 0.64 A out of it). The relatively short Ta—A1 distances are comparable to those found in other transition metal aluminum complexes (Ta—Al 2.79-3.13 A). The hydrogen atoms have not been located, but were evidenced by chemical and spectroscopic techniques (IR 1605, 1540 cm 1 HNMR 16.30p.p.m.). The Ta—(ju-H2)A1 unit is relatively stable, and (54) is inert to carbon monoxide or trimethylamine. It is a poor catalyst in the isomerization of 1-pentene. Formation of complexes analogous to (54) may explain the low yields often obtained from alkoxoaluminohy-drides and metal halides. 

Catalysts. It was shown by Friedel and Crafts that while aluminum chloride is a very active alkylation catalyst, other metal chlorides (ferric chloride, zinc chloride, etc.) are also effective. They also showed that other aluminum halides (aluminum... 

Reactive metal halides are known to add to unsaturated compounds to form 1,2 halometal compounds. Addition of boron and aluminum halides is of particular interest. 

Aluminum can accept two electrons to complete its octet. The pair of electrons is available from the halogen. An alkali halide can supply the electrons and form a complex (c), or the electron pair may come from the halogen of another aluminum chloride. Association with other aluminum halides accounts for the higher melting point of aluminum halides over antimony(lll) halides which have a formula weight of 95 or more. The association of aluminum sulfate, alkali metal sulfate, and water to form the stable alums is one of the more complex examples. 

Lewis Acid-Complexed Metal Salts. Mixtures of aluminum chloride and metal chloride are known to be active for the isomerization of paraffins at room temperature.178 Ono and co-workers179-183 have shown that the mixtures of aluminum halides with metal sulfates are much more selective for similar reactions at room temperature. 

Additives are also used to improve the solubility of halide donors [382, 383]. Metal(II) halides such as magnesium chloride, calcium chloride, barium chloride, manganese chloride, zinc chloride and copper chloride etc. are used as halide sources. In order to increase the solubility of the halides they are reacted with electron donors which have been previously described for the increase of solubility of Nd-components [338,339]. The number of catalyst components is further increased if two Al-compounds (alumoxane + aluminum (hydrido) alkyl) are used. In addition, a small amount of diene can also be present during the preformation of the different catalyst components as described by JSR. In some catalyst systems the total number of components reaches up to eight [338,339]. Such complex catalyst systems are also referred to in other JSR patents [384,385] (Sect. 2.2.6). 

A further error in IL synthesis can originate from purification processes. In order to remove the often yellowish color of ionic liquids after synthesis they are commonly purified over silica or alumina powder (see above). Once we obtained a liquid where the supplier invested a lot of effort to deliver Endres-quality . [EMIMJTFSA was made with the best available educts in the add-base routine from diluted aqueous [EMIMJOH and H-TFSA. This approach exdudes metal and halide impurities. The supplier removed the slight yellowish color by purification over silica. For this purpose the supplier used quite a fresh silica, which had not been used in any purification process before. One has to bear in mind that the dominant impurities, even in hiqh quality silica, are aluminum species. Figure 11.26 shows the 1st, the 7th and the 15th cydes of this liquid on Au(l 11). Apparently... 

The eutectic mixtures of the other aluminum halides with alkali halides also have low melting points (of about 100°C). The phase diagram of the A1C13-NaCl system is given in Figure 40 [390], The phase diagrams of A1C13 mixtures with other alkali metal chlorides have similar shapes. 

In alkylations of metal halides with A1R3 usually only one alkyl group is transferred, since the dialkyl aluminum halides are much less powerful alkylating agents than the trialkyls. The alkylaluminums react with compounds having acidic hydrogen atoms to give the alkane in some cases alkylation may occur, for example,... 

The chemistry of Lewis acids is quite varied, and equilibria such as those shown in Eqs. (28) and (29) should often be supplemented with additional possibilities. Some Lewis acids form dimers that have very different reactivities than those of the monomeric acids. For example, the dimer of titanium chloride is much more reactive than monomeric TiCL (cf., Chapter 2). Alkyl aluminum halides also dimerize in solution, whereas boron and tin halides are monomeric. Tin tetrachloride can complex up to two chloride ligands to form SnCL2-. Therefore, SnCl5 can also act as a Lewis acid, although it is weaker than SnCl4 [148]. Transition metal halides based on tungsten, vanadium, iron, and titanium may coordinate alkenes, and therefore initiate polymerization by either a coordinative or cationic mechanism. Other Lewis acids add to alkenes this may be slow as in haloboration and iodine addition, or faster as with antimony penta-chloride. 

Strong acids are able to donate protons to a reactant and to take them back. Into this class fall the common acids, aluminum halides, and boron trifluoride. Also acid in nature are silica, alumina, aluminosilicates, metal sulfates and phosphates, and sulfonated ion exchange resins. They can transfer protons to hydrocarbons acting as weak bases. Zeolites are dehydrated aluminosilicates with small pores of narrow size distribution, to which is due their highly selective action since only molecules small enough to enter the pores can react. 

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