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Solid-state molecular Organometallic Chemistry of Group 7 Carbonyls: Taming Reactive Complexes in an Anionic Cage


Project Description

Background:
Organometallic synthesis, reactivity and catalysis is nearly always carried out in solution, where the complex (or catalyst) of interest is dissolved in a solvent of choice (e.g. CH2Cl2). While this is convenient, it often means that very reactive intermediates in catalysis, or complexes in synthesis, are challenging to observe, let alone isolate – as the solvent often binds, or irreversibly reacts, with the metal centre. The Weller group has recently developed a new technique to avoid solvent binding, and thus isolate, characterise and study highly reactive complexes that cannot be made by traditional solution routes. The technique is deceptively simple: all the chemistry, characterisation, reactivity and even catalysis is carried out in a single–crystal, using no solvent. By using single–crystal to single–crystal transformations, gases penetrate the crystal and react with the reactive metal centre encapsulated in the crystal lattice to generate the target complex, or undergo the catalytic transformation of interest. We term this solid–state molecular organometallic chemistry (SMOM-Chem).[1,2] For example this approach allows incredibly reactive alkane complexes to be synthesized. These are key, but only short-lived in solution, intermediates in C-H activation process. We can do this because of a stabilising “nanoreactor” of anions around a reactive cation in the crystal lattice. The power of this approach is demonstrated by the synthesis on gram scale of alkane complexes that are indefinitely stable at room temperature, compared to lifetimes in solution that are (at best) minutes at temperatures of –100ºC. SMOM techniques thus allow for the isolation of “impossible” complexes.

Objectives:
Up until now this chemistry has focussed on group 9 (Co, Rh, Ir) complexes. The question is can SMOM chemistry be extended to other transition metals in the periodic table, and can, very reactive, synthetically challenging, and catalytically interesting, systems be developed? We will answer this in an exciting new project that combines SMOM techniques (Weller) with group 7 cations (Mn, Re) using photophysical methods (Lynam) to generate and interrogate the reactive metal centres.[3]

Experimental Approach:
Very recently, the design rules for stable SMOM systems have been determined. Informed by these criteria new cationic Mn- or Re-carbonyl complexes will be synthesised and their reactivity studied in the single-crystal, e.g. [M(chelating-ligand)(CO)n]+. A wide variety of ligand–types (chelate, pincer, non–innocent ligands) will be used to generate a library of new group-7 SMOM systems. These new complexes may be coordinatively unsaturated (with agostic interactions) or can be activated in-crystal by CO-loss using photolysis. These highly reactive 16 or 14-electron species are primed for reactivity in solid/gas processes, as well as being highly reactive “drop-in” catalysts for solution processes. In addition to the fundamental structure/bonding in these systems (i.e. responses to unsaturation) there is much exciting reactivity to explore, e.g. alkane, H2, noble-gas complexes, C-H activation and solid/gas catalysis. The project also offers the opportunity to study kinetics in solid-state using time-resolved infra-red spectroscopy.

Novelty:
The study of group-7 SMOM-chem, and their photophysical properties, is novel. The resulting chemistry is of interest to the organometallic, organic, heterogeneous and bioinorganic communities and industry. It will push the boundaries of what is achievable in synthetic chemistry, developing new types of synthesis (SMOM-photochem) and unlocking new catalytic systems.

Training:
The PhD student will become an expert in a wide range of techniques: air–sensitive organometallic synthesis, NMR (solution and solid-state), x-ray crystallography and new photophysical techniques, and will be supported by the larger team in the Weller/Lynam groups. There will be plenty of opportunities to explore solid/gas catalysis (batch and flow), interact with industry and to become familiar with cutting-edge computational techniques (in collaboration with Prof Macgregor, Heriot–Watt).

All Chemistry research students have access to our innovative Doctoral Training in Chemistry (iDTC): cohort-based training to support the development of scientific, transferable and employability skills: https://www.york.ac.uk/chemistry/postgraduate/idtc/

Equality and Diversity
The Department of Chemistry holds an Athena SWAN Gold Award and is committed to supporting equality and diversity for all staff and students. The Department strives to provide a working environment which allows all staff and students to contribute fully, to flourish, and to excel: https://www.york.ac.uk/chemistry/ed/. This PhD project is available to study full-time or part-time (50%).

This PhD will formally start on 1 October 2020. Induction activities will start on 28 September.

Funding Notes

Fully funded for 3 years by either the Engineering and Physical Sciences Research Council or Chemistry Teaching Studentship and cover: (i) a tax-free annual stipend at the standard Research Council rate (£15,009 for 2019-20), (ii) tuition fees at the UK/EU rate, (iii) funding for consumables. You do not need to apply separately for the EPSRC funding. However you need to submit a separate Teaching Studentship application: View Website

Teaching studentships are available to any student who is eligible to pay tuition fees at the home rate: View Website
ESPRC Studentships are available to any student who meets the EPSRC eligibility criteria: View Website

References

[1] Alasdair I. Mckay, Alexander J. Bukvic,* Bengt E. Tegner, Arron L. Burnage,* Antonio Martinez–Martinez, Nicholas H. Rees, Stuart A. Macgregor, Andrew S. Weller, J. Am. Chem. Soc. 2019, 141, 11700
[2] A. J. Martínez-Martínez, B. E. Tegner, A. I. McKay, A. J. Bukvic,* N. H. Rees, G. J. Tizzard, S. J. Coles, M. R. Warren, S. A. Macgregor and A. S. Weller, J. Am. Chem. Soc. 2018, 140, 14958
[3] L. A. Hammarback, I. P. Clark, I. V. Sazanovich, M. Towrie, A. Robinson, F. Clarke, S. Meyer, I. J. S. Fairlamb and J. M. Lynam, Nature Catal., 2018, 1, 830.

Candidate selection process:
• Applicants should submit a PhD application to the University of York by 8 January 2020
• Supervisors may contact candidates either by email, telephone, web-chat or in person
• Supervisors can nominate up to 2 candidates to be interviewed for the project
• Nominated candidates will be invited to a panel interview at the University of York in the week commencing 10 February 2020
• The awarding committee will award studentships following the panel interviews
• Candidates will be notified of the outcome of the panel’s decision by email

How good is research at University of York in Chemistry?

FTE Category A staff submitted: 47.06

Research output data provided by the Research Excellence Framework (REF)

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