Pseudochalcogenes

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Pseudochalcogenes are compounds that are similar in their properties to the elements of the sixth main group , the chalcogens ("ore formers"). Like the pseudohalogens, they belong to the so-called pseudo -elements and are also called "element-homologous compounds". Typical is the strong electron-withdrawing effect that z. B. as with some pseudohalides caused by nitrile groups (-CN). In contrast to the monovalent pseudohalides, the pseudochalcogenides are divalent.

Discovery story

While the halogen-analogous character of the pseudohalides was described as early as 1925, the group of their analogues for the chalcogenides has only been named such since 1971. This knowledge arose as a result of investigations into the complex formation and reactivity of the pseudohalides dicyanamide [N (CN) 2 ] - and tricyanomethanide [C (CN) 3 ] - as well as independent work on metal carbonyls.

Typical representatives of the pseudochalcogenides

Typical representatives of the pseudochalcogenide ions are the cyanamide ion NCN 2− and the dicyanomethanide ion C (CN) 2 2− . The atomic groups of these ions can, for. B. replace oxygen in cyanates , carbonates , carboxylates , nitrates , phosphates or sulfonates . With regard to the CH acidity and the reactivity at the second carbon atom, for example, malononitrile can be understood as a water-analogous molecule. According to the pseudochalcogen concept, tetracyanoethylene and azocarbodinitrile can be understood as molecular pseudochalcogenes. In analogy to molecular oxygen , they are comparatively strong oxidizing agents . The central double bond and the dienophilicity associated with it confirm the similarity of their reactivity to that of singlet oxygen .

Individual evidence

  1. ↑ AM Golub, H. Köhler et al .: Chemie der Pseudohalogenide (Berlin 1979)
  2. ^ A b H. Köhler: The pseudochalkogen concept - a contribution to the chemistry of element-homologous compounds, Nova Acta Leopoldina NF 59, 264 (1985), 259-276.
  3. ↑ L. Birckenbach et al .: Ber. German Chem. Ges. 58, 786 (1925), 2377.
  4. ↑ H. Koehler: Z. Chem. 11 (1971), 385.
  5. ^ H. Köhler, B. Seifert: J. Organometal. Chem. 12: 253-255 (1968).
  6. ↑ H. Köhler: Wiss. Z. Univ. Hall 18, 1 (1969), 33-46.
  7. ^ JE Ellis: J. Organometal. Chem. 86 (1971), 1.
  8. ↑ H. Köhler, U. Grobe: Wiss. Z. Univ. Hall 39, 2 (1990), 3-25.