A High‐Valent Non‐Heme μ‐Oxo Manganese(IV) Dimer Generated from a Thiolate‐Bound Manganese(II) Complex and Dioxygen

This study deals with the unprecedented reactivity of dinuclear non‐heme MnII–thiolate complexes with O2, which dependent on the protonation state of the initial MnII dimer selectively generates either a di‐μ‐oxo or μ‐oxo‐μ‐hydroxo MnIV complex. Both dimers have been characterized by different techniques including single‐crystal X‐ray diffraction and mass spectrometry. Oxygenation reactions carried out with labeled 18O2 unambiguously show that the oxygen atoms present in the MnIV dimers originate from O2. Based on experimental observations and DFT calculations, evidence is provided that these MnIV species comproportionate with a MnII precursor to yield μ‐oxo and/or μ‐hydroxo MnIII dimers. Our work highlights the delicate balance of reaction conditions to control the synthesis of non‐heme high‐valent μ‐oxo and μ‐hydroxo Mn species from MnII precursors and O2. Thiolate is the key: Dinuclear MnII–thiolate complexes display an unprecedented reactivity: direct O2 activation to generate dinuclear high‐valent oxo Mn species, including a di‐μ‐oxo MnIV dimer. Depending on the experimental conditions, the oxidized Mn species are different. A mechanism based on theoretical calculations is discussed to rationalize all experimental data.