A New Thiolate-Bound Dimanganese Cluster as a Structural and Functional Model for Class Ib Ribonucleotide Reductases

In class Ib ribonucleotide reductases (RNRs) a dimanganese(II) cluster activates superoxide (O-2(center dot-)) rather than dioxygen (O-2), to access a high valent Mn-III-O-2-Mn-IV species, responsible for the oxidation of tyrosine to tyrosyl radical. In a biomimetic approach, we report the synthesis of a thiolate-bound dimanganese complex [Mn-2(II)(BPMT)(OAc)(2)](ClO)(4) (BPMT=(2,6-bis{[bis(2-pyridylmethyl)amino]methyl}-4-methylthiophenolate) (1) and its reaction with O-2(center dot-) to form a [(BPMT)MnO2Mn](2+) complex 2. Resonance Raman investigation revealed the presence of an O-O bond in 2, while EPR analysis displayed a 16-line S-t=1/2 signal at g=2 typically associated with a (MnMnIV)-Mn-III core, as detected in class Ib RNRs. Unlike all other previously reported Mn-O-2-Mn complexes, generated by O-2(center dot-) activation at Mn-2 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.

Automated summary

In class Ib ribonucleotide reductases (RNRs), a dimanganese(II) cluster activates superoxide (O-2(center dot-)) to form a high valent Mn-III-O-2-Mn-IV species responsible for the oxidation of tyrosine. A thiolate-bound dimanganese complex [Mn-2(II)(BPMT)(OAc)(2)](ClO)(4) was synthesized as a biomimetic model for RNRs and proved to be a capable oxidant in aldehyde deformylation and phenol oxidation reactions.