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Structural formula
Category: Ferrocyphene
Surname Ferrocyphene
other names
  • Dicyanobis (1,10-phenanthroline) iron (II)
  • Bis (o-phenantroline) iron (II) cyanide
  • Bis (cyano-C) bis (1,10-phenantroline-N1, N10) iron
Molecular formula C 26 H 16 FeN 6
Brief description

Dark purple, almost black crystals

External identifiers / databases
CAS number
  • 23425-29-8 (dihydrate)
  • 14768-11-7 (trihydrate)
Wikidata Q1407959
Molar mass
  • 504.33 g mol −1 (dihydrate)
  • 522.34 g mol −1 (trihydrate)
Physical state


safety instructions
GHS labeling of hazardous substances
06 - Toxic or very toxic


H and P phrases H: 301
P: ?
As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .

In Ferrocyphen is complex -bound iron (II), which two (1.10) - phenanthroline ligands and two cyanide ion is coordinated. This forms an electrically neutral chelate complex .

Ferrocyphene serves as a redox indicator in redox titrations (e.g. nitritometry ) , as the color of the complex changes from yellow (Fe 2+ , ferrocyphene) to purple (Fe 3+ , ferricyphene) through oxidation .

It is also used in the titration of weak bases in non-aqueous media and for aromatic diazotization titrations.


The best representation in the laboratory is the displacement of 1,10-phenanthroline ligands (phen) from the tris (1,10-phenanthroline) iron (II) cation by cyanide ions.


Other ways, such as the displacement of cyanide ions by phenanthroline, are significantly slower and in lower yield. The direct combination of an iron (II) solution with equimolar amounts of potassium cyanide and 1,10-phenanthroline initially provides a mix of different complexes whose rearrangement to the desired product takes too long to be practical.

See also

Individual evidence

  1. a b c Alfred A. Schilt: Dicyanobis (1,10-phenanthroline) iron (II) and Dicyanobis (2,2'-bipyridine) iron (II) . In: Robert W. Parry (Ed.): Inorganic Syntheses . tape 12 . McGraw-Hill, Inc., 1970, ISBN   07-048517-8  ( defective ) , p. 247 ff . (English).
  2. Template: CL Inventory / not harmonized There is not yet a harmonized classification for this substance . A labeling of bis (cyano-C) bis (1,10-phenanthroline-N1, N10) iron in the Classification and Labeling Inventory of the European Chemicals Agency (ECHA), accessed on November 14, 2016, is reproduced from a self-classification by the distributor .
  3. P. Patnaik: Dean's analytical chemistry handbook , Irwin / McGraw Hill, 2nd edition, 2004, p. 4.71. ISBN 0-07-141060-0 .
  4. ^ Alfred A. Schilt: Mixed ligand complexes of iron (ii) as nonaqueous acid-base and aqueous oxidation-reduction indicators . In: Analytica Chimica Acta . tape 26 , p. 134-143 , doi : 10.1016 / s0003-2670 (00) 88359-2 .
  5. AA Schilt, JW Sutherland: A Reversible Internal Indicator for Sodium Nitrate Titrations. In: Analytical Chemistry . tape 36 , no. 9 , May 1, 2002, pp. 1805-1807 , doi : 10.1021 / ac60215a032 .