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Two mononuclear nonheme iron(II)-benzoylformate (BF) complexes [(6Me 2 -Me-BPA)Fe(BF)](ClO 4 ) (1a) and [(6Me 3 -TPMM)Fe(BF)](ClO 4 ) (1b) of tridentate nitrogen donor ligands, bis((6-methylpyridin-2-yl)methyl)( N -methyl)amine (6Me 2 -Me-BPA) and tris(2-(6-methyl)pyridyl)methoxymethane (6Me 3 -TPMM), were isolated and characterized. The structural characterization of iron(II)-chloro complexes indicates that the ligand 6Me 2 -Me-BPA binds to the iron(II) centre in a meridional fashion, whereas 6Me 3 -TPMM behaves as a facial ligand. Both the ligands were functionalized with terminal thiol for immobilization on gold nanoparticles (AuNPs), and the corresponding iron(II) complexes [(6Me 2 -BPASH)Fe(BF)(ClO 4 )]@C 8 Au (2a) and [(6Me 3 -TPMSH)Fe(BF)(ClO 4 )]@C 8 Au (2b) were prepared to probe the effect of immobilization on their ability to perform bioinspired oxidation reactions. All the complexes react with dioxygen to display the oxidative decarboxylation of the coordinated benzoylformate, but the complexes supported by 6Me 3 -TPMM and its thiol-appended ligand display faster reactivity compared to their analogues with the 6Me 2 -Me-BPA-derived ligands. In each case, an electrophilic iron-oxygen oxidant was intercepted as the active oxidant generated from dioxygen. The immobilized complexes (2a and 2b) display enhanced O 2 -dependent reactivity in oxygen-atom transfer reactions (OAT) and hydrogen-atom transfer (HAT) reactions compared to their homogeneous congeners (1a and 1b). Furthermore, the immobilized complex 2b displays catalytic OAT reactions. This study supports that the ligand geometry and immobilization on AuNPs influence the dioxygen-dependent reactivity of the complexes.

Two monoanionic nickel complexes Bu4N[Ni(LSeO)2] (1) and Bu4N[Ni(LSO)2] (2) (H2LSeO = 3,5-di-tert-butyl-2-hydroxyselenophenol and H2LSO = 3,5-di-tert-butyl-2-hydroxythiophenol) were synthesised by reductive cleavage of the respective 2,2'-dichalcogenobis(4,6-di-tert-butylphenol) (H2LX-X; X = Se, S) with nickel(ii) salts. The crystal structures of 1 and 2 confirm the reductive X-X bond cleavage with the concomitant formation of the corresponding monoanionic square planar complex, where quinoidal distortions of the aromatic rings are observed. The monoanionic complexes (1 and 2) are paramagnetic (S = 1/2), exhibiting rhombic EPR signals, and the g anisotropies are well correlated with the spin-orbit coupling of chalcogenides. The spectral data indicate that the ligands H2LXO in 1 and 2 are redox non-innocent and stabilise the square planar S = 1/2 nickel complexes with a highly delocalised unpaired electron. DFT calculations further support the delocalised electronic structures of the nickel complexes.