The three Unisyscat Groups (Hildebrandt, Dau and Ray) reveal in two joint publications the vital role of sulfur as non-innocence ligand in the catalytic reduction of dioxygen to hydrogen peroxide and in mimicking the reactivity of class Ib ribonucleotide reductases (RNRs).
Evidence of Sulfur Non‐Innocence in [Co (dithiacyclam)] ‐Mediated Catalytic Oxygen Reduction Reactions, B. Battistella, L. Iffland‐Mühlhaus, M. Schütze, B. Cula, U. Kuhlmann, H. Dau, P. Hildebrandt, T. Lohmiller, S. Mebs, U. Apfel, K. Ray, Angewandte Chemie International Edition 2022, 62, 10.1002/anie.2022140
In many metalloenzymes, sulfur-containing ligands participate in catalytic processes, mainly via the involvement in electron transfer reactions. In a biomimetic approach, the the implication of S-ligation in cobalt mediated oxygen reduction reactions (ORR) was demonstrated. A comparative study between the catalytic ORR capabilities of the four-nitrogen bound [Co(cyclam)]2+ (1,cyclam=1,5,8,11-tetraaza-cyclotetradecane) and the S-containing analog [Co(S2N2-cyclam)]2+ (2, S2N2-cyclam=1,8-dithia-5,11-diaza-cyclotetradecane) reveals improved catalytic performance once the chalcogen is introduced in the Co coordination sphere. Trapping and characterization of the intermediates formed upon dioxygen activation at the CoII centers in 1 and 2 point to the involvement of sulfur in the O2 reduction process as the key for the improved catalytic ORR capabilities of 2
A New Thiolate‐Bound Dimanganese Cluster as a Structural and Functional Model for Class Ib Ribonucleotide Reductases, B. Battistella, T. Lohmiller, B. Cula, P. Hildebrandt, U. Kuhlmann, H. Dau, S. Mebs, K. Ray, Angewandte Chemie International Edition 2023, 10.1002/anie.202217076
In class Ib ribonucleotide reductases (RNRs) a dimanganese(II) cluster activates superoxide (O2⋅−) rather than dioxygen (O2), to access a high valent MnIII−O2−MnIV species, responsible for the oxidation of tyrosine to tyrosyl radical. In a biomimetic approach, we report the synthesis of a thiolate-bound dimanganese complex [MnII2(BPMT)(OAc)2](ClO)4 (BPMT=(2,6-bis{[bis(2-pyridylmethyl)amino]methyl}-4-methylthiophenolate) (1) and its reaction with O2⋅− to form a [(BPMT)MnO2Mn]2+ complex 2. Unlike all other previously reported Mn−O2−Mn complexes, generated by O2⋅− activation at Mn2 centers, 2 proved to be a capable electrophilic oxidant in aldehyde deformylation and phenol oxidation reactions, rendering it one of the best structural and functional models for class Ib RNRs