Redox Isomerism in Main‐Group Chemistry: Tin Complex with <i>o</i>‐Iminoquinone Ligands

Abstract

The bis‐chelate tin complex 1 , based on the 4,6‐di‐ tert ‐butyl‐ N ‐( tert ‐butyl)‐ ortho ‐aminophenol ligand and representing the first example of a redox‐isomeric compound in main‐group chemistry, is synthesized and characterized by X‐ray diffraction analysis. Complex 1 exists in two electromeric forms in nonpolar solvents: a diamagnetic pseudotetrahedral (AP) 2 Sn IV ( 1a ) and a paramagnetic tetragonal‐pyramidal structure of low‐valence tin (imSQ) 2 Sn II ( 1b ) (where AP and imSQ are the dianionic and radical‐anionic forms of the ligand, respectively). The reversible redox‐isomeric rearrangement between 1a and 1b is investigated in solution by means of magnetochemistry, EPR spectroscopy, UV/Vis spectroscopy, and 119 Sn Mössbauer spectroscopy. This interconversion can be quenched by an addition of a strong donor ligand, such as pyridine (Py), resulting in an octahedral complex (AP) 2 Sn IV (Py) 2 ( 2 ) that does not undergo redox isomerism.