A New Family of One-Dimensional Conductors Derived from Magnus Green-Type Salts [Pt(NH3)4][PtX4] (X=Cl,Br): Class II and III Mixed-Valence Chains in a Double Chain Structure

A family of coloured compounds having metallic lustre and crystallizing as needles has been synthetized by controlled oxidation of Magnus green salt [Pt(NH3)4][ PtCl4] (MGS) and Magnus green-type salt [ Pt(NH3)4] [ PtBr4] in aqueous HClO4 or HBF4. Experimental evidences show that all these compounds are single-phase materials having tetragonal structure and containing two types of mixed-valence platinum chains (of class IIIb and class II respectively1) with chain axis as the c axis: (a) Class IIIb, valency delocalized Pt⋯pt chains where Pt is in a non-integral (presumably 2.33) oxidation state. These chains (α chains) are partially oxidized MGS-like chains with a Pt-Pt intrachain distance (= c/2) ranging from 2.85 to 2.92 A depending on the kind of complex; (b) Class II, with partially delocalized valencies, halogen-bridged Pt(II)⋯Y-Pt(IV) chains (Wolffram’s type β chains with Y=Cl,Br, I).