Aluminium chloride, structure

Diborane has a qeometric structure similar to that of dimeric aluminium chloride, namely... 

The solid anhydrous halides of some of the transition metals are often intermediate in character between ionic and covalent their structures are complicated by (a) the tendency of the central metal ion to coordinate the halide ions around it, to form an essentially covalent complex, (b) the tendency of halide ions to bridge, or link, two metal ions, again tending to covalency (cf. aluminium chloride, p. 153 and iron(III) chloride, p. 394). 

The ester and catalj st are usually employed in equimoleciilar amounts. With R =CjHs (phenyl propionate), the products are o- and p-propiophenol with R = CH3 (phenyl acetate), o- and p-hydroxyacetophenone are formed. The nature of the product is influenced by the structure of the ester, by the temperature, the solvent and the amount of aluminium chloride used generally, low reaction temperatures favour the formation of p-hydroxy ketones. It is usually possible to separate the two hydroxy ketones by fractional distillation under diminished pressure through an efficient fractionating column or by steam distillation the ortho compounds, being chelated, are more volatile in steam It may be mentioned that Clemmensen reduction (compare Section IV,6) of the hj droxy ketones affords an excellent route to the substituted phenols. 

Not surprisingly, the dipole moments of 1 1-complexes of phosphines and aluminium chloride are very large. Triethylphosphine also forms a 2 1 complex whose very low dipole moment suggests a symmetrical structure such as (139). ... 

Shore, S. G., and R. W. Parry Chemical Evidence for the Structure of the Diammoniate of Diborane , III. The Reactions of Borohydride Salts with Eithium Halides and Aluminium Chloride. J. Amer. chem. Soc. 80, 12 (1958). 

Other common examples are aluminium chloride, tin(rv) chloride, zinc chloride, etc. We shall, at this point, be concerned essentially with proton acids, and the effect of structure on the strength of a number of organic acids and bases will now be considered in turn. Compounds in which it is a C—H bond that is ionised will be considered subsequently (p. 270), however. 

Yoshino reports a novel and general method for the C-3 acylation of indoles with acyl chlorides in the presence of dialkylaluminium chloride which obviates the need for prior N-protection . Interestingly, as described in this preliminary communication, the unprotected indoles 147 are first treated with the Lewis acids prior to addition of the acid chlorides, yielding the desired 3-acyl derivatives 148. In reactions more typical of indoles under acidic conditions, Nakatsuka determined the structures of the dimers and trimers of 1-trimethylacetylindole produced in the presence of aluminium chloride . 

A new route to the tetrahydroTTF system is provided by reaction of oxalyl chloride with ethanedithiol followed by dehydration to give 35. When this is treated with aluminium chloride the salt 36 is formed and its X-ray structure is reported <00ZN(B)597>. The preparation of new simple benzoditelluroles 37 has been described <00MI1127>. Treatment of allyl dithiocarbamates 38 with bromine affords the 2-amino-l,3-dithiolanylium salts 39 <97MIP112282, 98MIP113243>. 

As mentioned in the introduction, recent synthetic developments now allow access to the 1,2-thiazine structure via disconnection type C (Figure 23). This process can be accomplished by a Friedel-Crafts-type cyclization of sulfamoyl chlorides. The initial report of this reaction utilized a stoichometric amount of aluminium chloride promoter <19920PP463>. Recently, however, A -ethyl phenethylsulfamoyl chloride 214 was shown to undergo Friedel-Crafts cyclization to form sultam 215 with just a catalytic amount of In(OTf)3 (Equation 33) <2002SL1928>. 

Benzene may be polymerized under the action of aluminium chloride and copper chloride into a thermostable structure which retains the chemical reactivity of benzene. Such a polymer may be sulfonated or phosphonated in suspension, and active acidic catalysts are obtained that are stable up to 350 °C and carry the functional groups only at the surface n°) ... 

Well-defined catalysts with isolated mononuclear metal species have also been obtained from reactions of diethylaluminium compounds with calix[4]-arenediols. For instance, a catalyst such as (25,27-dimethoxy-p-t-butylcalix[4]-arene-26,28-diolato)aluminium chloride [(dmca)AlCl], characterised by a rigid structure of the AIO4 moiety like a distorted trigonal bypyramid, forms a monomeric species in a benzene solution at freezing temperature. It has been successfully applied for propylene oxide and cyclohexene oxide polymerisations, leading to bifunctional low molecular weight polyethers of relatively... 

Next step of this synthesis consisted in the conversion of alcohol (17) to pisiferic acid (1) and this has been described in Fig. (3). The alcohol (17) in hexane was treated with Pb(OAc)4 in presence of iodine at room temperature to obtain the epoxy triene (19) (51%) whose structure was confirmed by spectroscopy. Treatment of (19) with acetyl p-toluene-sulfonic in dichloromethane yielded an olefinic acetate (20) and this was hydrogenated to obtain (21). The compound (22) could be isolated from (21) on subjection to reduction, oxidation and esterification respectively. The conversion of (22) to (23) was accomplished in three steps (reduction with sodium borohydride, immediate dehydration in dichloromethane and catalytic hydrogenation). Demethylation of (23) with anhydrous aluminium bromide and ethanethiol at room temperature produced pisiferic acid (1). Similar treatment of (23) with aluminium chloride and ethanethiol in dichloromethane yielded methylpisiferate (3). 

Chemical Modifications to Pitch. The earlier attempts to improve the commercial value of pitch residues must have been essentially exploratory research. Sanada et al, (71) in 1973 methylated the hydroxyl groups of 3,5-dimethyl phenol formaldehyde resin and noted, on carbonization, the formation of spheres of mesophase, the original resin giving an optical texture of mosaics in resultant carbons. Mochida et al. (72) carbonized naphthalene, anthracene and pyrene with aluminium chloride, sodium and potassium and examined the structure of the resultant carbons by optical microscopy and high resolution, fringe-imaging transmission electron microscopy (TEM),... 

The compound between aluminium chloride and ammonia, AlGl3 NH3, is remarkably stable and may be distilled without decomposition at 400° G. The energy of the A1—N bond in AlGl3 NH3, AlBrg NHg and All3 NH3 have been found to be 40, 38 and 30 kcals respectively . Evidently resonance exists between the following valence bond structures... 

Analogous structures will contribute to the resonance of AlC HgS, PHg GuHal and PH3 AlHalg. In the complexes formed between aluminium chloride and unsaturated hydrocarbons, valence bond structures are possible in which the aluminium becomes negatively charged with respect to a carbon atom, i.e. 

An unusual ionic structure, [(Me2N)2P]+AlCl4, is assigned to the 1 1 adduct of aluminium chloride and bis(dimethylamino)chlorophosphine.361 The phosphorus atom in the cation is clearly shown to be again two-coordinate and to be involved in p -p bonding to nitrogen. 

---