The mixed-valence Au'/Au"' complex [Au(CH,)~PP~,],B~, has been prepared by two methods: reduction of [ A u ( C H , )~P P~, ]~B~~ with AgCN; oxidation of [ A U ( C H~)~P P~~]~( C N ) , by Br,, followed by spontaneous reduction. The CH2CI2 solvate of the mixed-valence complex was characterized crystallographically: orthorhombic, Pcmn (nonstandard setting of Pnma, No. 62), a = 1 1.404 (2) A, 6 = 12.627 (2) A, c = 23.355 (3) A, V = 3363 ( 1 ) A', and 2 = 4. It consists of an eight-membered metallacycle containing a two-coordinate Au' and a four-coordinate Au"' centers. The X-ray photoelectron spectroscopy study of this complex along with its Au'/Au' and Au"'/Au"' congeners confirmed the crystallographic results.

No abstract

No abstract

Differential scanning calorimetry (DSC) demonstrates that compounds in the pseudobinary system Ag 2 S-Ag 2 Se undergo rapid, reversible solid-state phase changes at temperatures between approximately 70 and 178 °C. These temperatures vary systematically with composition, with highs at the pure end members, Ag 2 S (178 °C) and Ag 2 Se (134 °C), and a low in the compositional range of approximately Ag 2 S 0 .4Se 0 .6 to Ag 2 S 0 .3Se 0 .7 (70 °C). These data are consistent with the presence of two solid solutions in this system at ambient conditions: the Ag 2 S-III-type, monoclinic, ranging to approximately Ag 2 So.4Se o . 6 and the Ag 2 Se-II-type, orthorhombic, extending from Ag 2 Se to Ag 2 S 0 .3Se 0 .7. Entropies of transition of 6 to 9 e.u. characterize compositions within the Ag 2 S-III-type solid solution, whereas values of 13 to 16 e.u. mark members of the Ag 2 Se-II-type solid solution. The high-temperature allotrope is presumably a continuous solid solution between Ag 2 S-II and Ag 2 Se-I, which have similar body-centered cubic structures.

No abstract