CRYSTAL‐STRUCTURE OF RUTHENIUM RED AND STEREOCHEMISTRY OF ITS PECTIC STAIN

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Abstract
A crystal‐structure analysis of ruthenium red has indicated a composition of [Ru3Cl8 (OH)3 (NH3)12 (H2O)3]. Each ruthenium ion is coordinated cubically with at least eight chloride ions, and it is coordinated octahedrally with (1) four ammonia molecules in a square planar configuration and (2) either two water molecules or two hydroxyl ions in the axis perpendicular to that plane. The staining group is composed of the ruthenium ion and the associated square planar complex of four ammonia molecules. The staining site in the host molecule must have two negative charges 4.2 A apart and space to accommodate the staining group, lying with its plane perpendicular to the axis between these charges. It is shown that in pectic acid such a staining site occurs between each monomer unit and its next adjacent neighbor.
Funding Information
  • National Science Foundation (GB 4732)