Extreme molecules: Iron in its most unusual forms
For the first time, iron was synthesized in a molecule to give up seven electrons. The inert gas even helped bring about the unusual and completely unexpected reaction.
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As more and more electrons are gradually removed from them, the atoms begin to become aggressive.
Experts have now chemically produced an extreme version of iron, which is only found in the Sun in a similar form. The new compound contains an iron atom in the center that has donated seven electrons to its reactants. In common compounds, iron is oxidized only three times.
As reported by a team led by Carsten Mayer of the University of Erlangen-Nuremberg, it was created by allowing a highly unusual complex containing six-fold oxidized iron at the center to react with a highly reactive compound composed of the noble gases xenon and fluorine. According to the publication in Nature, the resulting molecule containing seven times more oxidized iron is only reasonably stable at temperatures below -50 degrees Celsius and reforms itself very quickly. Iron compounds that are extremely electron-poor can replace rare and expensive elements in chemical reactions, thus helping to save resources.
The iron atom has a total of 26 electrons, of which it gives up three quite easily and enters into a stable configuration with five outer electrons. This trivalent iron occurs, for example, in rust. But the more electrons are extracted from an atom, the greater its charge and attraction to the electrons of other atoms in the surrounding area. This is why iron compounds that are severely oxidized tend to steal electrons from other molecules. This willingness to give up and take up negative charges without making any changes is a desirable property in many chemical reactions. However, it also makes the materials developed by Mayer's team very unstable.
In the compounds developed by the working group, the iron is surrounded by partners, which in turn bind the electrons very strongly. The hexagonally oxidized iron, which the researchers also describe in the publication, is surrounded by a branched organic molecule that contains largely nitrogen: a single triple-bonded nitrogen atom and fluorine, the most electron-attracting element in the periodic table. Experts did not expect that even this molecule would give up an electron. But with the help of xenon fluoride, seven-fold oxidized iron was created in the center of the complex.
Iron oxidized six and seven times | Structures of the two new complexes, in which iron is surrounded by strong electron-withdrawing partners. Iron, which was oxidized six times, was previously known only from three other compounds.
This creates a molecule in which iron has formally given up more electrons than any other known chemical compound. The surrounding partners form bonds with the iron in which they share electrons – but they all belong to the partners. Therefore, they are not classical electron pair bonds, but rather called complex bonds. The fact that these complexes are so reactive shows that the iron atoms are in fact missing electrons. This is the first time that such a large number of electrons have been removed from an element through chemical reactions. Otherwise, iron with seven missing electrons is only found in very high-energy environments such as the Sun's magnetosphere In planetary nebulae, where high temperatures and strong magnetic fields separate electrons from the nucleus.
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