Magnus' green salt

Magnus' green salt is the chemical compound with the formula [Pt(NH₃)₄][PtCl₄]. This species has been of interest in materials chemistry and solid state physics because of its one-dimensional structure. It consists of a linear chain of Pt atoms separated by 3.25 Å.^[1] The Pt(II) centers are also coordinated to four molecules of ammonia and four chlorides, in an alternating manner. It is a semi-conductor.

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History

The salt was discovered by Heinrich Gustav Magnus in the early 1830's. It was one of the first examples of a metal complex of ammonia. Ammonia species are very common now - they were after all the basis of Alfred Werner's discoveries. MGS has the same empirical formula as cis-PtCl₂(NH₃)₂ ("Peyrone chloride") and trans-PtCl₂(NH₃)₂. These cis and trans compounds are molecules, whereas Magnus' green salt is a polymer.

Preparation

One mixes aqueous solutions of [Pt(NH₃)₄]²⁺ and [PtCl₄]^2-. A deep green precipitate appears. In recent years, it has been possible to generate soluble polymers by replacing the ammonia with ethylhexylamine.^[2][3]

References

1. ^ Atoji, M.; Richardson, J. W.; Rundle, R. E. "On the Crystal Structures of the Magnus Salts, Pt(NH₃)₄PtCl₄" Journal of the American Chemical Society, 1957, volume 79,pp 3017-3020; DOI: 10.1021/ja01569a009
2. ^ Caseri, W., "Derivatives of Magnus' green salt; from intractable materials to solution-processed transistors", Platinum Metals Review, 2004, volume 48, pages 91-100.
3. ^ Bremi, J.; Caseri, W. and Smith, P., "A new compound derived from Magnus' green salt: solid state structure and evidence for platinum chains in solution", Journal of Materials Chemistry, 2001, volume 11, pages 2593-2596.