Gallium benzene complexes

The gallium chloride complex, GaCU", reacts with Rhodamine B (formula 4.29), to form the ion pair which can be extracted from HCl medium into benzene or other solvents. The pink extract is the basis of a sensitive and selective method for the determination of gallium [20-22]. Addition of NaCI improves the extraction efficiency very effectively [22]. A mixture of benzene and diethyl ether, and also o-dichlorobenzene [23], have been recommended as extractants. Since Rhodamine B is only slightly soluble in o-dichlorobenzene, but dissolves readily in the meta-isomer, the o-dichlorobenzene must not be contaminated with the metaisomer. 

Reaction type (d) also complicates the Friedel-Crafts alkylation of benzene (a type db reaction, p. 141) by 1-bromopropane, MeCH2-CH2Br, in the presence of gallium bromide, GaBr3, as Lewis acid catalyst. The attacking electrophile is here a highly polarised complex,... 

The diphosphine-type ligands provide an opportunity for the complexation with group III and IV metals. For instance, the reaction of gallium or indium trihalides with l,2-bis-(diphenylphosphanyle)benzene (DP) leads to the formation of [(DP)2MC12]+[MX4] complexes. 

The most stable oxo-complexes are chelate compounds. Gallium and indium form tris- -diketone complexes, soluble in alcohol and benzene, and structurally similar to those of aluminium (Fig. 155). Gallium and thallium form trioxalato compounds like the oxalato-aluminates MJ[Ga ( 304)3]HgO. All the metals form tris-complexes with oxine (Fig. 156). 

Aluminum azide is obtained from reacting AICI3 with NaNs in THF, or from the reaction of A1H3-Et20 with HN3 in ether at low temperature. When trimethylamine adducts of alane are employed, solids thought to be azido complexes are produced (equation 7). Aluminium (and gallium) compounds X2M(N3), where X = Br or I, have been prepared by the reaction of MX3 with the halogen azide 7W3 in benzene. They are polymeric solids which show v(M—N3) modes near 490 cm" (M = Al), or 430 cm" (Ga) in the vibrational spectra. 

Phosphine oxide complexes with aluminium or gallium trimethyl can be made by direct addition to the etherate (9.159), while dimeric phosphinate complexes can be made by slowly adding a benzene solution of a phosphinic acid to a trialkyl aluminium (9.160, 9.161) [11,12]. Large cages are obtained in Equations 9.162 and 9.163 [13,14]. Compounds (9.164) have Ga-O-P linkages. 

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