MIXED-METAL CLUSTERS IN AQUEOUS-SOLUTION - REACTIONS OF TL-2(+) WITH AG+, CD2+, AND PB2+ AND OF ZN+ WITH TL+

Tl-2(+) is generated pulse radiolytically in 2 x 10(-2) M Tl+ solutions containing small concentrations of Ag+, Cd2+, and Pb2+ ions. The reaction of Tl-2(+) with Ag+ occurs with k = 3 x 10(9) M(-1) s(-1), the first product being a mixed cluster to which the structure (TlAg)(+) is attributed. It has strong absorption bands at 375 and 270 nm. The cluster rapidly reacts in a complex process with a second Ag+ ion (k 5 x 10(9) M(-1) s(-1)). Tl-2(+) reacts with Cd2+ with k = 9 x 10(7) M(-1) s(-1) to yield a product that absorbs below 250 nm. The reaction is shown to be not a simple electron transfer; formation of a cluster, possibly (CdTl)(2+), is proposed. Reaction of Tl-2(+) with Pb2+ consists of the transfer of an electron, k = 2 x 10(9) M(-1) s(-1). Zn+ transfers an electron to Tl+ with k = 5 x 10(9) M(-1) s(-1). These reactions are discussed in terms of the electrochemical potentials of the abnormal valence states of the metal ions involved.