Stereoelectronic Tuning of Bioinspired Nonheme Iron(IV)-Oxo Species by Amide Groups in Primary and Secondary Coordination Spheres for Selective Oxygenation Reactions.

Two mononuclear iron(II) complexes, [(6-amide-BPMEN)Fe](OTf) () and [(6-amide-Me-BPMEN)Fe(OTf)](OTf) (), supported by two BPMEN-derived (BPMEN = ,-dimethyl-,-bis(pyridine-2-yl-methyl)ethane-1,2-diamine) ligands bearing one or two amide functionalities have been isolated to study their reactivity in the oxygenation of C-H and C═C bonds using isopropyl 2-iodoxybenzoate (Pr-IBX ester) as the oxidant. Both and contain six-coordinate high-spin iron(II) centers in the solid state and in solution. The 6-amide-BPMEN ligand stabilizes an = 1 iron(IV)-oxo intermediate, [(6-amide-BPMEN)Fe(O)] ().

Hydrogen-atom and oxygen-atom transfer reactivities of iron(IV)-oxo complexes of quinoline-substituted pentadentate ligands.

A series of iron(II) complexes with the general formula [Fe()(L)] ( = 1, L = F, Cl; = 2, L = NCMe, HO) have been isolated and characterized. The X-ray crystallographic data reveals that metal-ligand bond distances vary with varying ligand field strengths of the sixth ligand. While the complexes with fluoride, chloride and water as axial ligand are high spin, the acetonitrile-coordinated complex is in a mixed spin state.

Tuning the stereoelectronic factors of iron(II)-2-aminophenolate complexes for the reaction with dioxygen: oxygenolytic C-C bond cleavage . oxidation of complex.

Oxidative C-C bond cleavage of 2-aminophenols mediated by transition metals and dioxygen is a topic of great interest. While the oxygenolytic C-C bond cleavage reaction relies on the inherent redox non-innocent property of 2-aminophenols, the metal complexes of 2-aminophenolates often undergo 1e-/2e- oxidation events (metal or ligand oxidation), instead of the direct addition of O2 for subsequent C-C bond cleavage. In this work, we report the isolation, characterization and dioxygen reactivity of a series of ternary iron(ii)-2-aminophenolate complexes [(TpPh,Me)FeII(X)], where X = 2-amino-4-tert-butylphenolate (4-tBu-HAP) (1); X = 2-amino-4,6-di-tert-butylphenolate (4,6-di-tBu-HAP) (2); X = 2-amino-4-nitrophenolate (4-NO2-HAP)(3); and X = 2-anilino-4,6-di-tert-butylphenolate (NH-Ph-4,6-di-tBu-HAP) (4) supported by a facial tridentate nitrogen donor ligand (TpPh,Me = hydrotris(3-phenyl-5-methylpyrazol-1-yl)borate).

Nickel complexes of ligands derived from (o-hydroxyphenyl) dichalcogenide: delocalised redox states of nickel and o-chalcogenophenolate ligands.

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.

Dioxygen reactivity of iron(ii)-gentisate/1,4-dihydroxy-2-naphthoate complexes of N4 ligands: oxidative coupling of 1,4-dihydroxy-2-naphthoate.

The influence of supporting ligands and co-ligands on the dioxygen reactivity of a series of iron(ii) complexes, [(6-Me-TPA)Fe(GN-H)] (1), [(6-Me-TPA)Fe(DHN-H)] (1a), [(BPMEN)Fe(GN-H)] (2), [(BPMEN)Fe(DHN-H)] (2a), [(TBimA)Fe(GN-H)] (3), and [(TBimA)Fe(DHN-H)] (3a) (GN-H = 2,5-dihydroxybenzoic acid and DHN-H = 1,4-dihydroxy-2-naphthoic acid) of N4 ligands, is presented. The iron(ii)-gentisate complexes react with dioxygen to afford the corresponding iron(iii) species. On the contrary, DHN-H undergoes oxidative C-C coupling to form [2,2'-binaphthalene]-1,1',4,4'-tetrone 3-hydroxy-3'-carboxylic acid (BNTHC) on 1a, and [2,2'-binaphthalene]-1,1',4,4'-tetrone 3,3'-dicarboxylic acid (BNTD) on 2a and 3a.

A High Spin Mn(IV)-Oxo Complex Generated via Stepwise Proton and Electron Transfer from Mn(III)-Hydroxo Precursor: Characterization and C-H Bond Cleavage Reactivity.

The oxomanganese(IV) complex [(dpaq)Mn(O)]-M (, M = redox-inactive metal ion, H-dpaq = 2-[bis(pyridin-2-ylmethyl)]amino--quinolin-8-ylacetamide), generated in the reaction of the precursor hydroxomanganese(III) complex with iodosylbenzene (PhIO) in the presence of redox-inactive metal triflates, has recently been reported. Herein the generation of the same oxomanganese(IV) species from using various combinations of protic acids and oxidants at 293 K is reported. The reaction of with triflic acid and the one-electron-oxidizing agent [Ru(bpy)] leads to the formation of the oxomanganese(IV) complex.

Highly Selective and Catalytic Oxygenations of C-H and C=C Bonds by a Mononuclear Nonheme High-Spin Iron(III)-Alkylperoxo Species.

The reactivity of a mononuclear high-spin iron(III)-alkylperoxo intermediate [Fe (t-BuL )(OOCm)(OH )] (2), generated from [Fe (t-BuL )(H O)(OTf)](OTf) (1) [t-BuL =1,1'-(((pyridin-2-ylmethyl)azanediyl)bis(ethane-2,1-diyl))bis(3-(tert-butyl)urea), OTf=trifluoromethanesulfonate] with cumyl hydroperoxide (CmOOH), toward the C-H and C=C bonds of hydrocarbons is reported. 2 oxygenates the strong C-H bonds of aliphatic substrates with high chemo- and stereoselectivity in the presence of 2,6-lutidine. While 2 itself is a sluggish oxidant, 2,6-lutidine assists the heterolytic O-O bond cleavage of the metal-bound alkylperoxo, giving rise to a reactive metal-based oxidant.

Iron(ii) complexes of 2-mercaptopyridine as rubredoxin site analogues.

The synthesis, characterization and reactivity studies of iron(ii) complexes [Fe(PySH)](OTf), 1-(OTf)2, [Fe(PySH)](ClO), 1-(ClO4)2, and [Fe(PyS)], (2), of a 2-mercaptopyridine (PySH) ligand are discussed. The X-ray crystal structures of both 1-(OTf)2 and 1-(ClO4)2 reveal a distorted tetrahedral geometry at the iron(ii) center with identical constituents. All the pyridine nitrogen atoms are protonated and thiolate ions are coordinated to the iron(ii) center.

Dioxygen Reactivity of an Iron Complex of 2-Aminophenol-Appended Ligand: Crystallographic Evidence of the Aromatic Ring Cleavage Product of the 2-Aminophenol Unit.

2-Aminophenol appended pentadentate ligand HGan was synthesized by mixing equimolar amounts of 2-[bis(2-pyridylmethyl)aminomethyl]aniline (A) and 3,5-di-tert-butyl catechol in hexane in the presence of EtN under air. The ligand reacted with Fe(ClO)·6HO or Fe(ClO)·6HO in the presence of tetrabutylammonium perchlorate, and EtN under air and provided a μ oxo-bridged dinuclear iron complex (1). X-ray single-crystal analysis of complex 1 revealed the presence of a furan derivative, resulting from the oxidative aromatic C-C bond cleavage product of 2-aminophenol derivative, in the coordination sphere of each iron center.