Tetrachloroaluminate ion

It is assumed that NaAlCl4 is dissociated into sodium and tetrachloroaluminate ions. Torsi and Mamantov [35] have investigated a further dissociation of the tetrachloroaluminate ion in molten sodium chloroaluminates by potentiometric studies. For the 50 50 mol% composition of NaCl-AlCl3 the principal anion is A1C14. In acidic melts it was assumed that the reaction A1C13 + A1C14 <-> A12C17 is quantitative. More important is the con-... 

STM has been used to examine the surface processes accompanying the near reversible wave (Ic, la) shown in Figure 16 [104]. High resolution imaging at 0.455 V revealed an ordered adlayer on the Cu(l 11) surface as shown in Figure 17. A possible model representing this structure corresponds to a layer of tetrachloroaluminate ions... 

Using a competition method, Lillya et a/.15,16 obtained relative reactivities for a series of substituted diene-tricarbonyliron compounds toward the methyloxocarbonium tetrachloroaluminate ion pair in di-chloromethane. The results are qualitatively summarized in Scheme 4. 

Table 21 Values of the Tetrachloroaluminate Ion Dissociation Constants for the Reaction... 

Scatterplots d vs. a and c 2 vs. a for sulfate, phosphate and tetrachloroaluminate ions are shown in Figure 6.10a,b,c. In every case, as the axial bond distance d increases, the central atom comes closer to the plane of the other three bonds, which become shorter. 

The mechanism of Friedel-Crafts acylation (shown next) resembles that fw alkylation, except that the carbonyl group helps to stabilize the cationic intermediate. The acyl halide forms a complex with aluminum chloride loss of the tetrachloroaluminate ion ( AICI4) gives a resonance-stabilized acylium ion. The acylium ion is a strong electrophile. It reacts with benzene or an activated benzene derivative to form an acylbenzene. 

Determination of equilibrium constants for the tetrachloroaluminate ion dissociation in ambient-temperature ionic liquids, Z.J.Kaurpinski and R.A.Osteryoung, Inorg. Chem., 1984, 1491. 

The other substitution reaction of benzene discussed in Chapter 10 was the chlorination of benzene. The mechanism of the chlorination of benzene also involves the formation of an active electrophile, CC. Anhydrous aluminium chloride, AICI3, is electron deficient because there are only six electrons around the central aluminium atom. This means it can act as a Lewis acid and attract a non-bonding pair of electrons from a molecule such as chlorine. The aluminium atom forms a dative covalent bond with one of the chlorine atoms in a chlorine molecule (Figure 20.38a). This triggers electron shifts to form a tetrachloroaluminate ion [AlCy and a positively charged chlorine ion (CL, a chloronium ion) - the aluminium chloride acts as a halogen carrier in this reaction. 

The powerful CT electrophile interacts with the % electrons of the benzene ring (Figure 20.38b) in the way described previously. The hydrogen ion formed reacts with the tetrachloroaluminate ion, forming hydrogen chloride and regenerating the halogen-carrier... 

A somewhat less obvious example of a Lewis acid—base reaction is the reaction of chloromethane with aluminum chloride to give a tetrachloroaluminate ion and a methyl carbocation, a potent Lewis acid. We will discuss this reaction in Chapter 13. 

Wood RH, D Oratio LA (1966) Lattice energy of Na tetrachloroaluminate and the heat of formation of the tetrachloroaluminate ion. Inorg Chem 5 682-894... 

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