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Late First-Row Transition Metal-Oxo Complexes for C–H Bond Activation

Periodic Reporting for period 4 - HurdlingOxoWall (Late First-Row Transition Metal-Oxo Complexes for C–H Bond Activation)

Reporting period: 2020-09-01 to 2022-02-28

The chemical, pharmaceutical, and materials industries rely heavily upon chemicals from oil and natural gas feed-stocks (saturated hydrocarbons) that require considerable functionalisation prior to use. Catalytic oxidative functionalisation (e.g. CH4 + [O] + cat. CH3OH), using first row transition metal catalysts, is potentially a sustainable, cheap, and green route to these high-commodity chemicals. However, catalytic oxidation remains a great modern challenge because such hydrocarbons contain remarkably strong inert C–H bonds that can only be activated with potent catalysts. We will take a Nature-inspired approach to designing and preparing powerful oxidation catalysts: we will interrogate the active oxidant, a metal-oxo (M=O) species, to guide our catalyst design. Specifically, we will prepare unprecedented Late first-row transition Metal-Oxo complexes (LM=O’s, LM = Co, Ni, Cu) that will activate the strongest of C–H bonds (e.g. CH4).

This will be accomplished using a family of novel low coordinate ligands that will support LM=O’s. Due to their expected potent reactivity we will prepare LM=O’s under unique oxidatively robust, low-temperature conditions to ensure their stabilisation. The poorly understood factors (thermodynamics, metal, d-electron count) that control the reactivity of M=O’s will be thoroughly investigated. Based on these investigations LM=O reactivity will be manipulated and optimised. We expect LM=O’s will be significantly more reactive than any early transition metal-oxo’s (EM=O’s), because they will display a greater thermodynamic driving force for C–H activation. It is thus expected that LM=O’s will be capable of the activation of the strongest of C–H bonds (i.e. CH4). Driven by the knowledge acquired from these investigations, we will design and prepare the next generation of molecular oxidation catalysts - a family of late first-row transition metal compounds capable of catalysing hydrocarbon functionalisation under ambient conditions.
The project has progressed along the expected lines proposed initially, with a number of important research breakthroughs listed below.

The first important discovery made was the identification of a facile means to tune the reactivity of high-valent oxidants (putative reactive species in oxidation catalysis) by simple anion exchange (changing the groups that interact with the metal). The second critical breakthrough was the demonstration that late transition metal oxidants are effective in PCET (whether an oxo-ligand ws rpesent or not). The third breakthrough in the project was the identification of the first examples of a high-valent metal-halide complex (Fe and Ni chloride and fluoride complexes) capable of performing hydrogen atom transfer oxidation (again, a process often implicated in oxidation catalysis). All breakthroughs have opened new avenues for late transition metal oxidation catalysis and the field of oxidation catalysis as a whole. The latter, halide-based oxidation, could open up the field of oxidation catalysis to oxo-free catalysis in the future and the oxidative halogenation of inert hydrocarbons.

Rapid Iron(III)-Fluoride Mediated Hydrogen Atom Transfer,
Chakadola Panda, Lorna M. Doyle, Robert Gericke, Aidan R. McDonald*, Angew. Chem. Int. Ed. 2021, 60, 26281-26286. https://onlinelibrary.wiley.com/doi/10.1002/anie.202112683

Comparing Metal–Halide and −Oxygen Adducts in Oxidative C/O–H Activation: AuIII–Cl versus AuIII–OH,
Marta Lovisari, Robert Gericke, Brendan Twamley, Aidan R. McDonald*, Inorg. Chem. 2021, 60, 15610–15616. https://pubs.acs.org/doi/10.1021/acs.inorgchem.1c02222

Reactivity Properties of Mixed- and High-Valent Bis(μ-Hydroxide)-Dinickel Complexes,
Giuseppe Spedalotto, Marta Lovisari, Aidan R. McDonald*, ACS Omega 2021, 42, 28162–28170. https://pubs.acs.org/doi/10.1021/acsomega.1c04225

Unexpected Intramolecular Phosphite-Mediated Amide Coupling To Yield 3,5-Dioxo-1-Piperazines,
Philipp Heim, Brendan Twamley, John O’Brien, Aidan R. McDonald*, ChemistrySelect 2021, 6, 9663-9668. https://chemistry-europe.onlinelibrary.wiley.com/doi/10.1002/slct.202102576

Oxo-Free Hydrocarbon Oxidation by an Iron(III)-Isoporphyrin Complex,
Robert Gericke, Lorna M. Doyle, Erik R. Farquhar, Aidan R. McDonald*, Inorg. Chem. 2020, 59, 13952-13961. https://pubs.acs.org/doi/abs/10.1021/acs.inorgchem.0c01618

Phenol Oxidation by a Nickel(III)-Fluoride Complex: Exploring the Influence of the Proton Accepting Ligand in PCET Oxidation,
Prasenjit Mondal, Aidan R. McDonald*, Chem. Eur. J. 2020, 26, 10083-10089. https://chemistry-europe.onlinelibrary.wiley.com/doi/10.1002/chem.202002135

Fast Hydrocarbon Oxidation by a High-Valent Nickel-Fluoride Complex,
Prasenjit Mondal, Marta Lovisari, Brendan Twamley, Aidan R. McDonald*, Angew. Chem. Int. Ed. 2020, 59, 13044-13050. https://onlinelibrary.wiley.com/doi/abs/10.1002/anie.202004639

Hydrogen atom transfer oxidation by a gold-hydroxide complex,
Marta Lovisari, Aidan R. McDonald*, Inorg. Chem. 2020, 59, 3659-3665. https://pubs.acs.org/doi/abs/10.1021/acs.inorgchem.9b03225

High-valent d7 NiIII versus d8 CuIII oxidants in PCET
Duenpen Unjaroen, Robert Gericke Marta Lovisari, Daniel Nelis, Prasenjit Mondal, Paolo Pirovano, Brendan Twamley, Erik R. Farquhar, Aidan R. McDonald*, Inorg. Chem. 2019, 58, 16838-16848. https://pubs.acs.org/doi/full/10.1021/acs.inorgchem.9b03101

Preparation and characterisation of a bis-μ-hydroxo-NiIII2 complex
Giuseppe Spedalotto, Robert Gericke, Marta Lovisari, Erik R. Farquhar, Brendan Twamley, Aidan R. McDonald*, Chem. Eur. J. 2019, 5, 11983-11990. https://onlinelibrary.wiley.com/doi/abs/10.1002/chem.201902812

Carboxamidate Ligand Noninnocence in Proton Coupled Electron Transfer
Caitilín McManus, Prasenjit Mondal, Marta Lovisari, Brendan Twamley, Aidan R. McDonald*, Inorg. Chem. 2019, 58, 4515-4523. https://pubs.acs.org/doi/10.1021/acs.inorgchem.9b00055

Hydrogen atom transfer by a high-valent nickel-chloride complex
Prasenjit Mondal, Paolo Pirovano, Ankita Das, Erik R. Farquhar, Aidan R. McDonald*, J. Am. Chem. Soc. 2018, 140, 1834–1841. https://pubs.acs.org/doi/10.1021/acs.chemmater.8b01454

Modulation of nickel pyridinedicarboxamidate complexes to explore the properties of high-valent oxidants
Paolo Pirovano, Brendan Twamley, Aidan R. McDonald*, Chem. Eur. J. 2018, 24, 5238-5245. http://dx.doi.org/10.1002/chem.201705203

Indirect evidence for a NiIII-oxyl oxidant in the reaction of a NiII complex with peracid
Paolo Pirovano, Abigail R. Berry, Marcel Swart, Aidan R. McDonald*, Dalton Trans. 2018, 47, 246-250. http://pubs.rsc.org/en/Content/ArticleLanding/2018/DT/C7DT03316H

Synthetic High-Valent M–O–X Oxidants
Paolo Pirovano, Aidan R. McDonald*, Eur. J. Inorg. Chem. 2018, 547–560. https://doi.org/10.1002/ejic.201701072

Tuning the reactivity of terminal nickel(III)-oxygen adducts for C–H bond activation
Paolo Pirovano, Erik R. Farquhar, Marcel Swart, Aidan R. McDonald*, J. Am. Chem. Soc. 2016, 138, 14362–14370. http://pubs.acs.org/doi/abs/10.1021/jacs.6b08406

Synthesis and Characterisation of a Mesocyclic Tripodal Triamine Ligand
Andrew D. Ure, Isabel Abánades Lázaro, Michelle Cotter, Aidan R. McDonald*, Org. Biomol. Chem. 2016, 14, 483-494. http://pubs.rsc.org/en/content/articlelanding/2015/ob/c5ob01556a#!divAbstract
Hydrogen Atom Transfer by Metal-halide
Tuning the Reactivity of High-Valent Oxidants