Radiocrystallographic study of KAuCl3.69Br0.31, KAuCl1.94Br2.06 and KAuCl1.82Br2.18,2H(2)O solid solutions.

The structures of anhydrous solid solutions KAuCl3.69Br0.31 (a=8.687(2) b=6 .420(1) c=12.290(1)Angstrom beta=95.568(3)degrees R=0.046) and KAuCl1.94Br0 .31 (a=8.789(2) b=6.578(1) c=12;562(2)Angstrom beta=96.147(3)degrees R=0.07 4) have been determined by X-ray diffraction to be in the P2(1)/c centrosym metric group. The structure of the hydrous solid solution KAuCl(1.82)Br(2.1 8)2H(2)O (a=9.414(1) b=11.842(1) c=8.399(2)Angstrom beta=94.459(2)degrees R =0.068) corresponds to the P2(1)/n group. The statistical substitution coef ficient observed in the anhydrous or hydrous solid solutions with a bromine /chlorine ratio near 50% gives proof of a trans substitution. In the anhydr ous solid solution KAuCl1.94Br2.06 the length between gold and halides (Hal ) is equal to 2.330(14)Angstrom for Au(2)-Hal(3) and 2.400(5)Angstrom for A u(2)-Hal(4), close to the corresponding lengths Au-Cl (2.288 Angstrom) in K AuCl4, 2H(28)O and Au-Br (2.42713) in KAuBr4, 2H(2)O. These results are in agreement with the existence of an intermediate trans entity [AuCl2Br2](-).