Magnus's green salt


Magnus's green salt is the inorganic compound with the formula . This salt is named after Heinrich Gustav Magnus, who, in the early 1830s, first reported the compound. The compound has an unusual structure, consisting of a chain of platinum atoms, and it exhibits unusual properties, being dark green, which is very unusual for platinum compounds.

Structure

This species has been of interest in materials chemistry and solid-state physics because of its one-dimensional structure. It contains a linear chain of alternating 2− anions and 2+ cations, in which the platinum atoms are separated by 3.25 Å. It is a semi-conductor.

Preparation

The compound may be prepared by combining aqueous solutions of 2+ and 2−, which gives a deep green solid precipitate. Under some conditions, this reaction affords a pink polymorph of Magnus's green salt. In this so-called "Magnus's pink salt", the square planar Pt complexes are not stacked.

Related compounds

Magnus's green salt has the same empirical formula as cis-PtCl22 and trans-PtCl22. These cis and trans compounds are molecules, whereas Magnus's green salt is a polymer. This difference is manifested by the solubility of the molecular complexes in water, whereas Magnus's green salt is insoluble.
Soluble analogues of Magnus's green salt can be prepared by replacing the ammonia with ethylhexylamine.
The corresponding palladium compound is known as "Vauquelin’s salt".

History

Magnus's green salt was one of the first examples of a metal ammine complex. Ammonia species are very common now: they were the basis of Alfred Werner's discoveries.