Juglophen: a tetradentate non-innocent electron sponge naphthoquinone-imine ligand and its reduced and oxidized nickel complexes [Ni(jp)]-,0,+

Henrik Schumann; Marius Klein; Christian Prinzisky; Olaf Burghaus; Jörg Sundermeyer

doi:10.1039/d1dt03927j

Juglophen: a tetradentate non-innocent electron sponge naphthoquinone-imine ligand and its reduced and oxidized nickel complexes [Ni(jp)]^-,0,+

Dalton Trans. 2022 Jun 21;51(24):9348-9356. doi: 10.1039/d1dt03927j.

Authors

Henrik Schumann¹, Marius Klein¹, Christian Prinzisky¹, Olaf Burghaus¹, Jörg Sundermeyer¹

Affiliation

¹ Department of Chemistry and Material Science Center, Philipps-Universität Marburg, Hans-Meerwein-Straße 4, 35032 Marburg, Germany. jsu@chemie.uni-marburg.de.

PMID: 35671192
DOI: 10.1039/d1dt03927j

Abstract

The synthesis of new tetradentate dianionic N₂O₂ ligand juglophen (H₂jp, 1) and its nickel(II) complex [Ni(jp)] (2) is reported. The unprecedented ligand synthesis is accomplished via oxidative coupling of 1,5-dihydroxynapthalene and o-phenylenediamine by hypervalent phenyliodine(III)-diacetate. Ligand 1 and complex 2 were characterized via NMR, IR, UV-Vis spectroscopy, mass spectrometry, cyclic voltammetry and by XRD analysis. In order to investigate the non-innocent character of ligand 1, [Ni(jp)] (2) was oxidized using AgPF₆ to form [Ni(jp)]⁺ [PF₆]^- (3) whereas one-electron reduction with [Cp₂Co] generated [Cp₂Co]⁺[Ni(jp)]^- (4). The paramagnetic nature of the oxidized and reduced species 3 and 4 was validated via EPR spectroscopy and further investigated pursuing DFT calculations at the PBE-D3(BJ)/def2-TZVPP level of theory. Predominantly ligand-centered SOMOs of 3 and 4 are allowing insight towards a deeper understanding of the redox behavior of [Ni(jp)] (2).