Dynamic behavior in solution of seven-coordinated transition metal complexes

•This topic has not been so far previously reviewed.•Some processes imply changes in the coordination geometry of the metal.•Considering the positions of the ligands, they migrate and/or they scramble.•Establishing rules about the dynamic behavior is so far not possible.•This review could encourage and help future researchers to get into this field.

This work reviews the dynamic behavior in solution of seven-coordinated complexes of different transition metals containing mono and polydentate monohapto ligands. The complexes are classified according to their geometry in the solid state, established by X-ray diffraction: pentagonal bipyramidal (PBP), capped octahedral (cO), capped trigonal prismatic (cTP), and complexes with 4:3 tetragonal base-trigonal base geometry (4:3). For each geometry, the processes are ordered from lower degrees of freedom to higher, thus going from complexes containing more polydentate ligands to those with more monodentate ligands. The processes detected in solution may be classified into two main groups: those implying changes in the coordination geometry of the metals, and those affecting the positions of the ligands. No changes in the coordination geometry of the starting or final products of the dynamic process are usually observed, but the proposal of intermediates of different geometries to that of the starting or final products is common. Two main different types of processes may be differentiated considering the positions of the ligands involved in the dynamic processes: migration and scrambling, and both occur for most of the dynamic processes herein reviewed.

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