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A Terminal FeIII-Oxo in a Tetranuclear Cluster: Effects of Distal Metal Centers on Structure and Reactivity.

ABSTRACT: Tetranuclear Fe clusters have been synthesized bearing a terminal FeIII-oxo center stabilized by hydrogen-bonding interactions from pendant ( tert-butylamino)pyrazolate ligands. This motif was supported in multiple Fe oxidation states, ranging from [FeII2FeIII2] to [FeIII4]; two oxidation states were structurally characterized by single-crystal X-ray diffraction. The reactivity of the FeIII-oxo center in proton-coupled electron transfer with X-H (X = C, O) bonds of various strengths was studied in conjunction with analysis of thermodynamic square schemes of the cluster oxidation states. These results demonstrate the important role of distal metal centers in modulating the reactivity of a terminal metal-oxo.

SUBMITTER: Reed CJ

PROVIDER: S-EPMC7207158 | biostudies-literature | 2019 Jun

REPOSITORIES: biostudies-literature

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A Terminal FeIII-Oxo in a Tetranuclear Cluster: Effects of Distal Metal Centers on Structure and Reactivity.

Reed Christopher J CJ Agapie Theodor T

Journal of the American Chemical Society 20190610 24

Tetranuclear Fe clusters have been synthesized bearing a terminal FeIII-oxo center stabilized by hydrogen-bonding interactions from pendant ( tert-butylamino)pyrazolate ligands. This motif was supported in multiple Fe oxidation states, ranging from [FeII2FeIII2] to [FeIII4]; two oxidation states were structurally characterized by single-crystal X-ray diffraction. The reactivity of the FeIII-oxo center in prot ...[more]

PMID: 31083986

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Project description:The oxo- and catecholate-bridged UIV/UIV Pacman complex [{(py)UIVOUIV(μ-O2C6H4)(py)}(LA)] A (LA = a macrocyclic "Pacman" ligand; anthracenylene hinge between N4-donor pockets, ethyl substituents on meso-carbon atom of each N4-donor pocket) featuring a bent UIV-O-UIV oxo bridge readily reacts with small molecule substrates to undergo either oxo-atom functionalisation or substitution. Complex A reacts with H2O or MeOH to afford [{(py)UIV(μ-OH)2UIV(μ-O2C6H4)(py)}(LA)] (1) and [{(py)UIV(μ-OH)(μ-OMe)UIV(μ-O2C6H4)(py)}(LA)] (2), respectively, in which the bridging oxo ligand in A is substituted for two bridging hydroxo ligands or one bridging hydroxo and one bridging methoxy ligand, respectively. Alternatively, A reacts with either 0.5 equiv. of S8 or 4 equiv. of Se to provide [{(py)UIV(μ-η2:η2-E2)UIV(μ-O2C6H4)(py)}(LA)] (E = S (3), Se (4)) respectively, in which the [E2]2- ion bridges the two UIV centres. To the best of our knowledge, complex A is the first example of either a d- or f-block bimetallic μ-oxo complex that activates elemental chalcogens. Complex A also reacts with XeF2 or 2 equiv. of Me3SiCl to provide [{(py)UIV(μ-X)2UIV(μ-O2C6H4)(py)}(LA)] (X = F (5), Cl (6)), in which the oxo ligand has been substituted for two bridging halido ligands. Reacting A with either XeF2 or Me3SiCl in the presence of O(Bcat)2 at room temperature forms [{(py)UIV(μ-X)(μ-OBcat)UIV(μ-O2C6H4)(py)}(LA)] (X = F (5A), Cl (6A)), which upon heating to 80 °C is converted to 5 and 6, respectively. In order to probe the importance of the bent UIV-O-UIV motif in A on the observed reactivity, the bis(boroxido)-UIV/UIV complex, [{(py)(pinBO)UIVOUIV(OBpin)(py)}(LA)] (B), featuring a linear UIV-O-UIV bond angle was treated with H2O and Me3SiCl. Complex B reacts with two equiv. of either H2O or Me3SiCl to provide [{(py)HOUIVOUIVOH(py)}(LA)] (7) and [{(py)ClUIVOUIVCl(py)}(LA)] (8), respectively, in which reactions occur preferentially at the boroxido ligands, with the μ-oxo ligand unchanged. The formal UIV oxidation state is retained in all of the products 1-8, and selective reactions at the bridging oxo ligand in A is facilitated by: (1) its highly nucleophilic character which is a result of a non-linear UIV-O-UIV bond angle causing an increase in U-O bond covalency and localisation of the lone pairs of electrons on the μ-oxo group, and (2) the presence of the bridging catecholate ligand, which destabilises a linear oxo-bridging geometry and stabilises the resulting products.

Dataset Information

A Terminal FeIII-Oxo in a Tetranuclear Cluster: Effects of Distal Metal Centers on Structure and Reactivity.

Publications

A Terminal Fe<sup>III</sup>-Oxo in a Tetranuclear Cluster: Effects of Distal Metal Centers on Structure and Reactivity.

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