School of Chemistry

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Charlotte Willans

University Research Fellow
Member of the Process Research and Development group

Contact details

Room: 1.16
Tel: +44 (0)113 3435868
Email: C.E.Willans@leeds.ac.uk

Keywords

N-Heterocyclic carbenes
Electrochemical synthetic methodology
Flow technology
Catalysis
Anticancer

Photograph of Charlotte Willans

Research interests

N-Heterocyclic carbenes (NHCs) are stable singlet carbenes that can act as excellent two electron donor ligands towards elements across the whole periodic table. They have received wide attention in transition metal chemistry and have a plethora of catalytic and biomedical applications. However, the use of NHCs in industry is still relatively limited due, in part, to their non-trivial synthetic procedures. We are developing novel synthetic routes to metal-NHCs which rely on electrochemistry rather than harsh basic conditions. Coupled with the translation into electrochemical flow reactors (Figure 1), we envisage metal-NHCs becoming more attractive for general use in important industrial processes.


Figure 1. Electrochemical flow reactor for the synthesis of metal-NHCs1

The electrochemical synthesis of metal-NHCs enables more elaborate functional groups to be incorporated into the ligand structure, allowing for finer control at the metal centre. We are interested in bringing together the two distinct and highly versatile ligand types, NHCs and carboranes, to take advantage of the unique properties of each moiety within one ligand structure.

We are involved in the development of metal-NHCs for both catalytic and biomedical applications. Our focus has been on copper-NHCs for catalysis, due to its lower cost and toxicity compared to precious metals, and the chemotherapeutic properties of silver-NHCs. We examine the reactivity of 'non-innocent' NHCs, as full mechanistic understanding of how these ligands behave will help in their design to prevent catalyst deactivation.

Useful links

Browse our research pages to find out more about the group and what we do.   
   
   

Publications

Allison SJ, Sadiq M, Baronou E, Cooper PA, Dunnill C, Georgopoulos NT, Latif A, Shepherd S, Shnyder SD, Stratford IJ, Wheelhouse RT, Willans CE, Phillips RM Preclinical anti-cancer activity and multiple mechanisms of action of a cationic silver complex bearing N-heterocyclic carbene ligands Cancer Letters 403 98-107, 2017
DOI:10.1016/j.canlet.2017.04.041
View abstract

Cookson NJ, Fowler JM, Martin DP, Fisher J, Henkelis JJ, Ronson TK, Thorp-Greenwood FL, Willans CE, Hardie MJ Metallo-cryptophane cages from cis-linked and trans-linked strategies Supramolecular Chemistry 1-12, 2017
DOI:10.1080/10610278.2017.1355055
View abstract

Chapman MR, Henkelis SE, Kapur N, Nguyen BN, Willans CE A Straightforward Electrochemical Approach to Imine- and Amine-bisphenolate Metal Complexes with Facile Control Over Metal Oxidation State ChemistryOpen 5 351-356, 2016
DOI:10.1002/open.201600019
View abstract

Younesi Y, Nasiri B, Babaahmadi R, Willans CE, Fairlamb IJS, Ariafard A Theoretical rationalisation for the mechanism of N-heterocyclic carbene-halide reductive elimination at CuIII, AgIIIand AuIII Chemical Communications 52 5057-5060, 2016
DOI:10.1039/c6cc01299j
View abstract

Holmes J, Pask CM, Fox MA, Willans CE Tethered N-heterocyclic carbene-carboranes: Unique ligands that exhibit unprecedented and versatile coordination modes at rhodium Chemical Communications 52 6443-6446, 2016
DOI:10.1039/c6cc01650b
View abstract

Fowler JM, Thorp-Greenwood FL, Warriner SL, Willans CE, Hardie MJ M12L8metallo-supramolecular cube with cyclotriguaiacylene-type ligand: Spontaneous resolution of cube and its constituent host ligand Chemical Communications 52 8699-8702, 2016
DOI:10.1039/c6cc04130b
View abstract

Chapman MR, Kwan MHT, King GE, Kyffin BA, Blacker AJ, Willans CE, Nguyen BN Rapid, metal-free and aqueous synthesis of imidazo[1,2-: A] pyridine under ambient conditions Green Chemistry 18 4623-4627, 2016
DOI:10.1039/c6gc01601d
View abstract

Holmes J, Pask CM, Willans CE Chelating N-heterocyclic carbene-carboranes offer flexible ligand coordination to IrIII, RhIIIand RuII: Effect of ligand cyclometallation in catalytic transfer hydrogenation Dalton Transactions 45 15818-15827, 2016
DOI:10.1039/c6dt02079h
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Lake BRM, Chapman MR, Willans CE N-Heterocyclic carbenes; Partakers not just spectators, 2016
DOI:10.1039/9781782623960-00107
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Hardie M, Fowler J, Thorp-Greenwood F, Willans C, Warriner S M12L8 metallo-supramolecular cube with cyclotriguaiacylene-type ligand: spontaneous resolution of cube and its constituent host ligand., 2016
DOI:10.5518/87

Chapman MR, Lake BRM, Pask CM, Nguyen BN, Willans CE Solid-state structure, solution-state behaviour and catalytic activity of electronically divergent C,N-chelating palladium-N-heterocyclic carbene complexes Dalton Transactions 44 15938-15948, 2015
DOI:10.1039/c5dt02194d
View abstract

Williams TJ, Bray JTW, Lake BRM, Willans CE, Rajabi NA, Ariafard A, Manzini C, Bellina F, Whitwood AC, Fairlamb IJS Mechanistic Elucidation of the Arylation of Non-Spectator N-Heterocyclic Carbenes at Copper Using a Combined Experimental and Computational Approach Organometallics 34 3497-3507, 2015
DOI:10.1021/acs.organomet.5b00093
View abstract

Mohamed HA, Lake BRM, Laing T, Phillips RM, Willans CE Synthesis and anticancer activity of silver(I)-N-heterocyclic carbene complexes derived from the natural xanthine products caffeine, theophylline and theobromine Dalton Transactions 44 7563-7569, 2015
DOI:10.1039/c4dt03679d
View abstract

Sherborne GJ, Chapman MR, Blacker AJ, Bourne RA, Chamberlain TW, Crossley BD, Lucas SJ, Mcgowan PC, Newton MA, Screen TEO, Thompson P, Willans CE, Nguyen BN Activation and deactivation of a robust immobilized Cp*Ir-transfer hydrogenation catalyst: A multielement in situ X-ray absorption spectroscopy study Journal of the American Chemical Society 137 4151-4157, 2015
DOI:10.1021/ja512868a
View abstract

Chapman MR, Pask CM, Ariafard A, Willans CE σ-Alkenyl endo-palladacycle formation via regiospecific functionalisation of an unreactive NHC-tethered C(sp2)-H bond Chemical Communications 51 5513-5515, 2015
DOI:10.1039/c4cc10163d
View abstract

Chapman MR, Shafi YM, Kapur N, Nguyen BN, Willans CE Electrochemical flow-reactor for expedient synthesis of copper-N-heterocyclic carbene complexes Chemical Communications 51 1282-1284, 2015
DOI:10.1039/c4cc08874c
View abstract

Lake BRM, Ariafard A, Willans CE Mechanistic insights into the oxidative coupling of N-heterocyclic carbenes within the coordination sphere of copper complexes. Chemistry - A European Journal 20 12729-12733, 2014
DOI:10.1002/chem.201404298
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Lake BRM, Willans CE Remarkable stability of copper(II)-N-heterocyclic carbene complexes void of an anionic tether Organometallics 33 2027-2038, 2014
DOI:10.1021/om500178e
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Mohamed HA, Willans CE Silver-N-heterocyclic carbene complexes as promising anticancer compounds, 2014
DOI:10.1039/9781849737692-00026
View abstract

Willans CE, Lake BRM Structural Diversity of Copper(I)-N-Heterocyclic Carbene Complexes; Ligand Tuning Facilitates Isolation of the First Structurally Characterised Copper(I)-NHC Containing a Copper(I)-Alkene Interaction Chemistry - A European Journal 19 16780-16790, 2013
DOI:10.1002/chem.201301896
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Bullough EK, Little MA, Willans CE Electrochemical synthesis of a tetradentate copper N-heterocyclic carbene calix[4]arene and its transmetalation to palladium: Activity of the palladium complex in Suzuki-Miyaura cross-coupling Organometallics 32 570-577, 2013
DOI:10.1021/om301085s
View abstract

Lake BRM, Bullough EK, Williams TJ, Whitwood AC, Little MA, Willans CE Simple and versatile selective synthesis of neutral and cationic copper(I) N-heterocyclic carbene complexes using an electrochemical procedure. Chem Commun (Camb) 48 4887-4889, 2012
DOI:10.1039/c2cc30862b
View abstract

Bullough EK, Kilner CA, Little MA, Willans CE Tetrakis(methylimidazole) and tetrakis(methylimidazolium) calix[4]arenes: competitive anion binding and deprotonation. Org Biomol Chem 10 2824-2829, 2012
DOI:10.1039/c2ob07025a
View abstract

Monteiro DCF, Phillips RM, Crossley BD, Fielden J, Willans CE Enhanced cytotoxicity of silver complexes bearing bidentate N-heterocyclic carbene ligands. Dalton Trans 41 3720-3725, 2012
DOI:10.1039/c2dt12399a
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Willans CE, French S, Anderson KM, Barbour LJ, Gertenbach J-A, Lloyd GO, Dyer RJ, Junk PC, Steed JW Tripodal imidazole frameworks: Reversible vapour sorption both with and without significant structural changes. Dalton Trans 40 573-582, 2011
DOI:10.1039/c0dt01011a
View abstract

Willans CE, Kilner CA, Fox MA Deboronation and deprotonation of ortho-carborane with N-heterocyclic carbenes. Chemistry 16 10644-10648, 2010
DOI:10.1002/chem.201001730

Willans CE N-heterocyclic carbene adducts of carborane ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY 239 -, 2010

Willans CE Non-transition metal N-heterocyclic carbene complexes In Organometallic Chemistry , 2010

Willans CE, French S, Barbour LJ, Gertenbach JA, Junk PC, Lloyd GO, Steed JW A catenated imidazole-based coordination polymer exhibiting significant CO2sorption at low pressure (Dalton Transactions (2009) (6480) DOI: 10.1039/b911265k) Dalton Transactions 10624-, 2009
DOI:10.1039/B923644A

Willans CE, French S, Barbour LJ, Gertenbach J-A, Junk PC, Lloyd GO, Steed JW A catenated imidazole-based coordination polymer exhibiting significant CO2 sorption at low pressure. Dalton Trans 6480-6482, 2009
DOI:10.1039/b911265k
View abstract

Willans CE, Anderson KM, Potts LC, Steed JW Allosteric effects in a tetrapodal imidazolium-derived calix[4]arene anion receptor. Org Biomol Chem 7 2756-2760, 2009
DOI:10.1039/b904148f
View abstract

Willans CE, Anderson KM, Paterson MJ, Junk PC, Barbour LJ, Steed JW Bis(N-heterocyclic carbene) Dipalladium Complexes: Synthesis, Solid-State Conformational Studies and Solution Behaviour EUR J INORG CHEM 2835-2843, 2009
DOI:10.1002/ejic.200900219

Willans CE, French S, Barbour LJ, Gertenbach JA, Junk PC, Lloyd GO, Steed JW A catenated imidazole-based coordination polymer exhibiting significant CO2 sorption at low pressure (pg 6480, 2009) DALTON T 10624-10624, 2009

Kerton FM, Holloway S, Power A, Soper RG, Sheridan K, Lynam JM, Whitwood AC, Willans CE Accelerated syntheses of amine-bis(phenol) ligands in polyethylene glycol or "on water" under microwave irradiation CAN J CHEM 86 435-443, 2008
DOI:10.1139/V08-043

Willans CE, Sinenkov MA, Fukin GK, Sheridan K, Lynam JM, Trifonov AA, Kerton FM Lanthanide chloride complexes of amine-bis(phenolate) ligands and their reactivity in the ring-opening polymerization of epsilon-caprolactone DALTON T 3592-3598, 2008
DOI:10.1039/b802219d

Dickson SJ, Paterson MJ, Willans CE, Anderson KM, Steed JW Anion binding and luminescent sensing using cationic ruthenium(II) aminopyridine complexes CHEM-EUR J 14 7296-7305, 2008
DOI:10.1002/chem.200800772

Willans CE, Fish C, Green M, Kilby RJ, Lynam JM, Russell CA, Whitwood AC Nucleophilic substitution reactions of the tricyclic triphosphorus cage P-3(CBut)(2): a novel route to polyphosphorus phosphenium complexes DALTON T 3422-3428, 2008
DOI:10.1039/b800864g

Murray P, Willans C, Bredenkamp MW, Gertenbach JA 2,4,6-Tris(bromomethyl)-1,3,5-trimethylbenzene ACTA CRYSTALLOGR E 63 O224-O225, 2007
DOI:10.1107/S1600536806052160

Willans CE, Anderson KM, Junk PC, Barbour LJ, Steed JW A small tris(imidazolium) cage forms an N-heterocyclic carbene complex with silver(I) CHEM COMMUN 3634-3636, 2007
DOI:10.1039/b708692j

Slattery JM, Fish C, Green M, Hooper TN, Jeffery JC, Kilby RJ, Lynam JM, McGrady JE, Pantazis DA, Russell CA, Willans CE Evidence for a S(N)2-type pathway for phosphine exchange in phosphine-phosphenium cations, [R2P-PR3 '](+) CHEM-EUR J 13 6967-6974, 2007
DOI:10.1002/chem.200601742

Kerton FM, Kozak CM, Luttgen K, Willans CE, Webster RJ, Whitwood AC Dimerisation versus polymerisation: Affects of donor position in isomeric dilithium diamine-bis(phenolate) complexes INORG CHIM ACTA 359 2819-2825, 2006
DOI:10.1016/j.ica.2005.11.013

Fish C, Green M, Jeffery JC, Kilby RJ, Lynam JM, McGrady JE, Pantazis DA, Russell CA, Willans CE Cationic phosphorus-carbon-pnictogen cages isolobal to [C5R5](+) CHEM COMMUN 1375-1377, 2006
DOI:10.1039/b517710c

Fish C, Green M, Kilby RJ, Lynam JM, McGrady JE, Pantazis DA, Russell CA, Whitwood AC, Willans CE A new reaction pathway in organophosphorus chemistry: Competing S(N)2 and AE ' pathways for nucleophilic attack at a phosphorus-carbon cage compound ANGEW CHEM INT EDIT 45 3628-3631, 2006
DOI:10.1002/anie.200504546

Fish C, Green M, Jeffery JC, Kilby RJ, Lynam JM, McGrady JE, Pantazis DA, Russell CA, Willans CE A main-group analogue of housene: The subtle influence of the inert-pair effect in group 15 clusters ANGEW CHEM INT EDIT 45 6685-6689, 2006
DOI:10.1002/anie.200601804

Fish C, Green M, Jeffery JC, Kilby RJ, Lynam JM, Russell CA, Willans CE A selective synthesis of the 1,3,4-triphospholide anion ORGANOMETALLICS 24 5789-5791, 2005
DOI:10.1021/om050766d

Ager D, van den Berg M, Minnaard AJ, Feringa BL, de Vries AHM, Willans CE, Boogers JAF, de Vries JG An affordable catalyst for the production of amino acids METHODOLOGIES IN ASYMMETRIC CATALYSIS 880 , 2004

Kerton FM, Whitwood AC, Willans CE A high-throughput approach to lanthanide complexes and their rapid screening in the ring opening polymerisation of caprolactone DALTON T 2237-2244, 2004
DOI:10.1039/b406841f

Willans CE, Mulders JMCA, de Vries JG, de Vries AHM Ligand-free palladium catalysed Heck reaction of methyl 2-acetamido acrylate and aryl bromides as key step in the synthesis of enantiopure substituted phenylalanines J ORGANOMET CHEM 687 494-497, 2003
DOI:10.1016/j.jorganchem.2003.09.012

de Vries AHM, Mulders JMCA, Willans CE, Schmieder-van de Vondervoort L, Parlevliet FJ, de Vries JG Heck reactions with homeopathic palladium. ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY 225 , 2003

van den Berg M, Minnaard AJ, Haak RM, Leeman M, Schudde EP, Meetsma A, Feringa BL, de Vries AHM, Maljaars CEP, Willans CE, Hyett D, Boogers JAF, Henderickx HJW, de Vries JG Monodentate phosphoramidites: A breakthrough in rhodium-catalysed asymmetric hydrogenation of olefins ADV SYNTH CATAL 345 308-323, 2003

Sherborne GJ, Adomeit S, Menzel R, Rabeah J, Bruckner A, Fielding MR, Willans CE, Nguyen BN Origins of High Catalyst Loading in Copper(I)-Catalysed Ullmann- Goldberg C-N Coupling Reactions Chemical Science -,
DOI:10.1039/C7SC02859H
View abstract