Reductive Nitric Oxide Coupling at a Dinickel Core: Isolation of a Key cis‐Hyponitrite Intermediate en route to N2O Formation. Issue 6 (9th January 2019)

• Record Type: Journal Article
• Authors: Ferretti, Eleonora; Dechert, Sebastian; Demeshko, Serhiy; Holthausen, Max C.; Meyer, Franc
• Is Part Of: Angewandte Chemie international edition. Volume 58:Issue 6(2019)
• Page Start: 1705
• Page End: 1709
• Publication Date: 2019-01-09
• Subjects: dinuclear complexes -- hyponitrite complexes -- nickel -- nitric oxide -- small molecule activation; Chemistry -- Periodicals; 540
• DOI: 10.1002/anie.201811925
• Languages: English
• ISSNs: 1433-7851

Abstract

Abstract: Reductive coupling of nitric oxide (NO) to give N2 O is an important reaction in the global nitrogen cycle. Here, a dinickel(II) dihydride complex 1 that releases H2 upon substrate binding and serves as a masked dinickel(I) scaffold is shown to reductively couple two molecules of NO within the bimetallic cleft. The resulting hyponitrite complex 2 features an unprecedented cis ‐[N2 O2 ] 2− binding mode that has been computationally proposed as a key intermediate in flavodiiron nitric oxide reductases (FNORs). NMR and DFT evidence indicate facile rotational fluxionality of the [N2 O2 ] 2− unit, which allows to access an isomer that is prone to N2 O release. Protonation of 2 is now found to trigger rapid N2 O evolution and formation of a hydroxido bridged complex, reminiscent of FNOR reactivity. This work provides fundamental insight into the biologically relevant reductive coupling of two NO molecules and the subsequent trajectory towards N2 O formation at bimetallic sites. Abstract : Emulated reaction trajectory : Two NO molecules are reductively coupled at a dinickel(II) dihydride complex that serves as a dinickel(I) synthon via substrate induced H2 release. The resulting cis ‐hyponitrite adopts an unusual N, O‐bridging binding mode in solid state, but facile rotational fluxionality within the bimetallic cleft allows to access an isomer that is prone to proton‐triggered N2 O formation.