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In most main group element compounds, the valence electrons of the isolated atoms combine to form chemical bonds that satisfy the octet rule. For instance, the four valence electrons of carbon overlap with electrons from four hydrogen atoms to form CH4. The one valence electron leaves sodium and adds to the seven valence electrons of chlorine to form the ionic formula unit NaCl (Figure 1a). Transition metals do not normally bond in this fashion. They primarily form coordinate covalent bonds, a...

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Preparation of SNS CobaltII Pincer Model Complexes of Liver Alcohol Dehydrogenase

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Coordination equilibria between seven- and five-coordinate iron(II) complexes.

Michaela Grau¹, Jason England, Rafael Torres Martin de Rosales

¹Department of Chemistry, Imperial College London , Exhibition Road, London, SW7 2AY, U.K.

Inorganic Chemistry

|October 12, 2013

Summary

Researchers discovered the first dynamic equilibrium between seven- and five-coordinate geometries in iron(II) complexes. This finding expands the known coordination chemistry of transition metals, revealing new possibilities for complex structures.

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Area of Science:

Inorganic Chemistry
Coordination Chemistry
Transition Metal Complexes

Background:

Common coordination geometries include octahedral, tetrahedral, and square planar.
Coordination equilibria between different geometries (e.g., six- and four-coordinate in nickel(II)) are known.
These equilibria are crucial for understanding metal complex behavior.

Purpose of the Study:

To report the first observation of a seven-five coordination equilibrium.
To investigate dynamic equilibria between different coordination geometries in iron(II) complexes.
To provide spectroscopic evidence for distinct geometric forms in solution.

Main Methods:

Solution-state spectroscopy was extensively employed.
Analysis focused on identifying and characterizing different coordination geometries.
Iron(II) complexes were synthesized and studied under various conditions.

Main Results:

Evidence for a dynamic equilibrium between two iron(II) complexes was established.
One complex exhibits a seven-coordinate pentagonal bipyramidal geometry.
The other complex displays a five-coordinate trigonal bipyramidal geometry.

Conclusions:

This study presents the first documented seven-five coordination equilibrium.
The findings expand the understanding of coordination diversity in transition metal chemistry.
Dynamic equilibria between disparate coordination numbers are possible in iron(II) systems.