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Complexes with unusual coordination numbers (C.N.) have always attracted attention of researches [1]; for gold(III), these C.N.s are 5 and 6. Data on the stability of gold(III) complexes with these C.N.s in aqueous solutions are scarce. Only in [2][3][4][5] were the constants of the addition of a fifth ligand (halide ion) to tetracoordinated complexes, , , and Au (En is ethylenediamine), determined. It was found that the contribution of the pentacoordinated complexes to the system material balance is relatively low even with high halide-ion concentrations. The electronic absorption spectrum of the complex was found to exhibit a new band [3]. This work continues the research into gold(III) complexes with C.N. > 4 and deals with spectrophotometric study of the complexation of chlorodiethylenetriaminegold(III) with chloride ions in aqueous solutions.The changes observed in the electronic spectrum of a solution of Au ( Dien ) Cl 3 (Dien is diethylenetriamine) in the presence of excess concentrations of chloride ions have been attributed [6,7] to the formation of gold(III) complexes with C.N. > 4. The possibility of existence of these complexes in aqueous solutions was noted in [8]; the C.N.(Au) in the crystal structure of Au ( Dien ) Cl 3 was found to be 6. The Raman spectrum of this complex displays a band at 258 cm -1 , which is retained in the spectrum of an aqueous solution (255 cm -1 ) and is missing from the spectrum of KAuCl 4 ; therefore, this band was attributed to the Au -Cl ax bond vibrations. In another study [9], this band was attributed to diethylenetriamine vibrations. The formation constants of gold(III) complexes with C.N. > 4 were not determined in the studies cited [6-8]. AuCl 4 -AuBr 4 -En ( ) 2 3+ AuBr 5 2- EXPERIMENTALReagent grade perchloric and hydrochloric acids and reagent grade sodium chloride were used. Sodium perchlorate was prepared by a known method [10]; diethylenetriamine trihydrochloride was obtained by neutralization of diethylenetriamine (Derk) with hydrochloric acid at T ~ 0°ë , the salt being isolated by treatment with ethanol and recrystallized from aqueous ethanol.The Au(Dien)Cl 3 complex was prepared by a known procedure [11] and recrystallized from aqueous ethanol.The experiments were carried out in an aqueous solution at T = 20 ± 1°ë and the ionic strength I = 1.0 mol/l maintained by NaClO 4 used as the supporting electrolyte. The electronic absorption spectra of solutions with constant concentrations of Au(III) complex and H + and a variable concentration of and Clwere recorded immediately after the preparation on a Specord UV-VIS spectrophotometer in quartz cells. An identical gold-free solution was placed in the reference cell. RESULTS AND DISCUSSIONIn a spectrophotometric study of the complexation between AuDienCl 2+ and Cl -(reaction 1), it is necessary to minimize the influence of side reactions that can For C 4 H 16 N 3 Cl 3 anal. calcd. (%):Abstract -The reaction of Au(Dien)Cl 2+ (Dien is diethylenetriamine) with the chloride ion was studied spectrophotometrically in...

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