Mixed Valence Chemistry and Metal Chain Compounds

Abstract

In 1896 Alfred Werner1 began to investigate what, at that time, were thought to be two isomeric forms of sodium bis-oxalatoplatinite. The curious feature which attracted Werner’s attention to these compounds was that while one was pale yellow, the other was copper red. He was soon able to show that they were not actually isomers at all, and that the yellow salt, which had the formula Na2Pt(C2O4)22H2O, could be converted into the red one only by partly oxidizing it with chlorine or bromine water. He also noted several other examples of platinum salts which likewise existed in pairs, one member being a simple divalent compound such as ()K or (PtCy4)K2 — to use his nomenclature — the other derivable fr m the first by partial oxidation. In every case the divalent compound was pale in colour while the partly oxidized one was very dark, frequently copper coloured, with the appearance of a metallic reflector: Werner had discovered the class of mixed valence platinum chain compounds about which so much has been written in the last few years, and whose properties form one of the principal topics of this Advanced Study Institute.