Yann Sarazin

ORCID: 0000-0003-1121-0292

Researcher ID: Q-2202-2015

Our research interests chiefly lie in the coordination and organometallic chemistry of main group metals. We are investigating fundamental aspects of the organometallic chemistry of group 2 and group 14 metals, and we are also keen on their applications in homogeneous catalysis towards a sustainable development. 

More specifically, we devise complexes built around the large alkaline-earth metals (calcium, strontium and barium) and tetrelenes (tin and lead). In many cases, we also seek to implement them as potent molecular precatalysts for atom-efficient transformations: ring-opening polymerisations of biosourced cyclic esters to produce biopolymers, as well as hydroelementation and heterodehydrocoupling reactions for the production of fine chemicals.

See below for a more detailed description of the four main topics that are currently captivating our attention

Bis(imino)carbazolate: a master key for barium chemistry
P. M. Chapple, S. Kahlal, J. Cartron, T. Roisnel, V. Dorcet, M. Cordier, J.-Y. Saillard,* J.-F. Carpentier, Y. Sarazin*
Angew. Chem. Int. Ed. 2020, accepted article. DOI: 10.1002/anie.202001439   Hot paper highlighted in ChemistryViews (link)

Barium-catalysed dehydrocoupling of hydrosilanes and borinic acids: A mechanistic insight
E. Le Coz, Z. Zhang, T. Roisnel, L. Cavallo, L. Falivene,* J.-F. Carpentier, Y. Sarazin*
Chem. Eur. J. 2020, 26, 3535. DOI: 10.1002/chem.201904933   Hot paper

Synthesis of bridged tetrahydrobenzo[b]azepines and derivatives through an aza‐Piancatelli cyclization/Michael addition sequence
S. Wang, R. Guillot, J.-F. Carpentier, Y. Sarazin, C. Bour, V. Gandon,* D. Lebœuf*
Angew. Chem. Int. Ed. 2020, 59, 1134-1138. DOI: 10.1002/anie.201911761

Lead(II) siloxides
A.-A. Someșan, E. Le Coz, C. I. Rat, V. Dorcet, T. Roisnel, C. Silvestru,* Y. Sarazin*
Chem. Eur. J. 2019, 25, 16236-16240. DOI: 10.1002/chem.201904713

Barium siloxides and catalysed formation of Si‐O‐Si’ motifs
E. Le Coz, S. Kahlal, J.-Y. Saillard,* T. Roisnel, V. Dorcet, J.-F. Carpentier, Y. Sarazin*
Chem. Eur. J. 2019, 25, 13509-13513. DOI: 10.1002/chem.201903676

Metal⋅⋅⋅F−C bonding in low‐coordinate alkaline earth fluoroarylamides
H. Roueindeji, A. Ratsifitahina, T. Roisnel, V. Dorcet, S. Kahlal, J.‐Y. Saillard,* J.‐F. Carpentier, Y. Sarazin*
Chem. Eur. J. 2019, 25, 8854-8864. DOI: 10.1002/chem.201901262   Hot paper

• Since 2008 CNRS Research Fellow, Institut des Sciences Chimiques de Rennes UMR 6226 CNRS – University of Rennes 1
• 2007-2008 Post-doc research associate (Prof. JF Carpentier), Institut des Sciences Chimiques de Rennes - UMR CNRS 6226 – University of Rennes 1
• 2004-2007 Post-doc research associate (Prof. M Bochmann), University of East Anglia (UK)

• 2012 (Oct.) Research Habilitation, University of Rennes, France
• 2004-2007 Post-doc research associate (Prof. M Bochmann), University of East Anglia (UK)
• 2000-2004 PhD in coordination and macromolecular chemistry. Supervisor Prof. M Bochmann, University of East Anglia, United Kingdom
• 1999-2000 MSc in organic and macromolecular chemistries, University of Lille, France
• 1995-1999 Undergraduate studies, University of Bordeaux, France

• More than 80 publications in international peer-reviewed journals, including: 1 Chem. Rev., 2 JACS, 6 Angew. Chem. Int. Ed., 20 Chem. Eur. J., 1 Chem. Rec., etc.
• h-index = 30
• 3000+ citations 
• 6 families of PCT Int. Appl. WO patents
• 5 book chapters
• 16 invited seminars in international universities
• 6 invited plenary and keynote lectures in international conferences
• 15 oral presentations in international conferences

• Agence Nationale de la Recherche (ANR): projects GreenLAkE, 2011-2015; Polcade, 2017-2021; Alcacat, 2017-2021
• Ministère de l’Enseignement Supérieur, de la Recherche et de l'Innovation: 2013, 2016, 2020
• European Union: Marie Skłodowska-Curie Actions grant, 2013

• Industrial partnership with Triskem International (2018-) 

We are actively involved in productive collaborations with several research groups across France, Europe and beyond:

• Luigi Cavallo and Laura Falivene, KAUST, Saoudi Arabia: DFT computations and reaction mechanisms
• François Ganachaud, INSA Lyon, France: alkaline earth metals and silicone materials (ANR POLCADE)
• Vincent Gandon, ICMMO Orsay, France: alkaline earth complexes in Lewis acidic catalysis (ANR ALCACAT)
• Florence Mongin, ISCR Rennes, France: s-block metals, structure and reactivity
• Hassan Oulyadi, COBRA Rouen, France: s-block metals and multinuclear NMR spectroscopy
• Jean-Yves Saillard and Samia Kahlal, ISCR Rennes, France: DFT computations and structural analysis
• Anca Silvestru, University Babeş-Bolyai, Cluj-Napoca, Romania: chalcogenates for main group metal complexes
• Cristi Silvestru, University Babeş-Bolyai, Cluj-Napoca, Romania: inorg./organometallic chemistry of lead(II)

Former or occasional collaborations: Manfred Bochmann (Norwich, UK), Michel Etienne (Toulouse, France), Chris Kozak (St John's, Canada), Danny Leznoff (Simon Fraser University, Canada), Laurent Maron (Toulouse, France), Tarun K. Panda (IIT Hyderabad, India), Sven Tobisch (Saint Andrews, UK), A. Trifonov (Moscow, Russia).

Besides, our group also maintains several partnerships with major industrial partners: Total Petrochemicals, Arkema, Bostik, Triskem International.

• Chairman and coordinator of GECOM-CONCOORD, Erquy, 2019
• Chairman and coordinator of Main Group Metal Chemistry Symposium, Rennes, 2018
• Chairman and coordinator of Journées Chimie de Coordination de la Société Chimique de France 2014, Rennes, 2014
• Member of the Advisory Board for the International Conference on Germanium, Tin and Lead
• Member of the editorial board of Main Group Metal Chemistry (since 2016)
• Scientific expert for international research agency (ACS Petroleum fund, UEFISCDI)
• External examiner for PhD theses

• Hanieh Roueindeji: PhD student, 2015- (organometallic chemistry of large alkaline earths)
• Joanna Hammoud: PhD student, 2017-2020 (large alkaline earths complexes for Lewis acid catalysis)
• Peter Chapple: PhD student, 2018-2021 (alkaline earth complexes: metal-metal bond and dehydrocoupling catalysis)
• Albert Soran: Postdoc, 2020 (functionalised polysilazanes by dehydropolymerisation catalysis with alkaline earth metals)
• Corina Stoian: MSc student, 2020 (metal-metal bonds with main group metals)

      PhD students

• Valentin Poirier: 2008-2011; NMR Research engineer, Structuralis, Paris, France
• Nicolas Maudoux: 2011-2014; Research engineer, Triskem International, Rennes, France
• Sorin Roşca: 2012-2015; PDRA UBC Vancouver, Canada (with L. L. Schafer)
• Clément Bellini: PhD 2013-2016; R&D engineer, Arkéma
• Erwann Le Coz: PhD student, 2016-2019; R&D engineer, Vinci Technologie

      Post-doctoral research associates

• Pierre de Frémont: 2008-2009; now CNRS Research Fellow, University of Strasbourg, France
• Liana Annunziata: 2009-2010; now Project manager, SICPA, Switzerland
• Amelia Cortes: 2009-2010; now Associate Professor, University of Rennes, France
• Bo Liu: 2010-2013; now Associate Professor, Changchun Institute of Applied Chemistry, PR China
• Lingfang Wang: 2011-2014; now Associate Professor, Yancheng, PR China
• Nuria Romero: 2015-2016; now Associate Professor, Autonomous University of Barcelona, Spain

      MSc students

• Dragos Roşca: 2010; PhD University of East Anglia, UK (with M. Bochmann)
• Sorin Roşca: 2012; PhD University of Rennes, France (with Y. Sarazin)
• Sami Fadlallah: 2014; PhD University of Lille, France (with M. Visseaux)
• Yuya Hu: 2015; PhD University of Geneva, Switzerland (with C. Mazet)
• Eric Tan: 2015; PhD Institute of Chemistry of Catalonia (ICIQ), Spain (with A. M. Echavarren)
• Fatima Abou Khalil: 2017
• Zeinab Farhat: 2018
• Jenani Louis: 2018-2019; PhD Max Planck Institute Mulheim, Germany (with A. Furstner)

Our main expertise is in the demanding, but also rewarding, chemistry of the heavier alkaline earths: calcium, strontium and barium. These are abundant, inexpensive main group metals that offer plenty of scope ! Yet, their high reactivity is a real challenge. 

Well-defined heteroleptic complexes of the large, oxophilic and electropositive alkaline earths are highly ionic and exhibit d⁰ electronic configurations. They display remarkable catalytic activities in a range of reactions: polymerisation, terminal alkyne coupling, hydrogenation and hydroelementation of alkenes, etc. Intimate knowledge of the structure of the precatalysts has opened up access to detailed mechanistic studies, a key to the improvement of catalyst performances. 

To overcome the problem of ligand redistribution in solution typical of these metals, we are utilising the bulky N(SiMe₃)₂ amido group, or more often its derivative N(SiMe₂H)₂. This allows the stabilisation of otherwise kinetically labile heteroleptic species thanks to intramolecular b-anagostic Met∙∙∙H–Si interactions. This has enabled the production of a myriad of Ca, Sr and Ba complexes supported by phenolato, alkoxo or N-containing (imino-anilide, diketiminate, carbazolate, etc.) ligands that are stable under conditions relevant to catalysis. The existence of Ae∙∙∙H–Si contacts in these complexes is attested to by XRD crystallography and NMR and FTIR spectroscopies; it is also backed up by state-of-the-art DFT computations.

In recent years, we have focused on the preparation of low-coordinate alkaline-earth complexes, where the coordination number does not exceed 3 or 4. Quite an achievement for these metals which love high coordination numbers! We have then taken full advantage of non-covalent, secondary interactions to generate highly electron-deficient alkaline earth complexes. Typically, we are using Met∙∙∙F, Met∙∙∙H-Si and/or Met∙∙∙C(pi) interactions to stabilise our compounds, and this has been rather successful! We have even achieved the synthesis of the first-ever two-coordinate barium complex, using a bulky boryloxide ligand. These results represent fundamental advances in the organometallic chemistry of the alkaline earths. Yet, the resulting complexes very often constitute excellent molecular catalysts for a plethora of reactions. 

Selected references for topic 1

(1) Bis(imino)carbazolate: a master key for barium chemistry
P. M. Chapple et al., Angew. Chem. Int. Ed. 2020, accepted article. DOI: 10.1002/anie.202001439

(2) Metal∙∙∙F-C bonding in low-coordinate alkaline earth fluoroarylamides
H. Roueindeji et al., Chem. Eur. J. 2019, 25, 8854. DOI: 10.1002/chem201901262

(3) Secondary interactions - Cement in trinuclear calcium complexes (invited article)
S.-C. Roşca et al., Inorg. Chim. Acta 2018, 475, 99. DOI: 10.1016/j.ica.2017.08.038

(4) Tethered cationic alkaline earth - olefin complexes
S.-C. Roşca et al., Dalton trans. 2017, 46, 14785. DOI: 10.1039/C7DT03300A

(5) pi-Ligands in alkaline earth complexes
S.-C. Roşca et al., Organometallics 2017, 36, 1269. DOI: 10.1021/acs.organomet.7b00006

(6) Alkaline earth-olefin complexes with secondary interactions
S.-C. Roşca et al., Chem. Eur. J. 2016, 22, 6505. DOI: 10.1002/chem.201601096

(7) Discrete, solvent-free alkaline-earth metal cations: Metal···fluorine interactions and ROP catalytic activity
Y. Sarazin et al., J. Am. Chem. Soc. 2011, 133, 9069. DOI: 10.1021/ja2024977

The catalysed heterofunctionalisation of unsaturated substrates is of tremendous interest, not least because of its atom efficiency in the construction of C-X bonds (X = N, P, O, etc.). Our calcium, strontium and barium complexes constitute excellent precatalysts for the inter- and intramolecular hydroamination of alkenes, hydrophosphination of activated alkenes and hydrophosphonylation of aldehydes and ketones. They range amongst the most effective to date for these catalysed reactions, converting large amounts of substrate in record time and under mild conditions.

Our alkaline-earth complexes also act as competent precatalysts for chemoselective dehydrocoupling reactions for the creation of  E-E' bonds between two heteroelements (E, E' = N, P, Si, B, etc.). They are particularly effective in the N-H/H-Si cross-dehydrocoupling of amines and hydrosilanes to generate original silazanes. The benchmark couplings of triphenylsilane with pyrrolidine or tert-butylamine has enabled us to delineate several key reactivity trends and highlight the extreme efficiency of barium catalysts. In fact, barium is the best metal for this type of catalysis by quite la large margin!

Following these seminal results, we became interested in other barium-promoted dehydrocouplings, such as the production of polycarbosilazanes from difunctional amines and hydrosilanes, the formation of borasiloxanes R₂BO-SiR'₃ from borinic acids and hydrosilanes, and also the production of asymetric siloxanes R₃Si-O-SiR'₃. All these reactions are not only very fast, but they also are chemoselective!

SELECTED PUBLICATIONS FOR TOPIC 2

(1) Barium-catalysed dehydrocoupling of hydrosilanes and borinic acids: A mechanistic insight
E. Le Coz et al., Chem. Eur. J. 2020, asap article. DOI: 10.1002/chem201904933

(2) Barium siloxides and catalysed formation of Si-O-Si' motifs
E. Le Coz et al., Chem. Eur. J. 2019, 25, 13509. DOI: 10.1002/chem201903676

(3) Low-coordinate barium boryloxides: synthesis and dehydrocoupling catalysis for the production of borasiloxanes
E. Le Coz et al., Angew. Chem. Int. Ed. 2018, 57, 11747. DOI: 10.1002/anie.201807297

(4) Sequential barium-catalysed N-H/H-Si dehydrogenative cross-couplings: cyclodisilazanes vs linear oligosilazanes
C. Bellini et al., Chem. Eur. J. 2016, 22, 15733. DOI: 10.1002/chem.201603191

(5) Tailored cyclic and linear polycarbosilazanes via barium-catalysed N-H/H-Si dehydrocoupling reactions
C. Bellini et al., Angew. Chem. Int. Ed. 2016, 55, 3744. DOI: 10.1002/anie.201511342

(6) Alkaline-earth catalysed cross-dehydrocoupling of amines and hydrosilanes: Reactivity trends, scope and mechanism
C. Bellini et al., Chem. Eur. J. 2016, 22, 4564. DOI: 10.1002/chem.201504316

(7) Barium-mediated cross-dehydrocoupling of hydrosilanes with amines - A complementary approach by theory and experiment
C. Bellini et al., Angew. Chem. Int. Ed. 2015, 54, 7679. DOI: 10.1002/anie.201502956

(8) When bigger is better: Intermolecular hydrofunctionalizations of activated alkenes catalyzed by heteroleptic alkaline-earth complexes
B. Liu et al., Angew. Chem. Int. Ed. 2012, 51, 4943. DOI: 10.1002/anie.201200364 

Growing concern towards environmental issues, depletion of the fossil feedstocks and unstable crude oil prices have prompted research groups to investigate the use of biopolymers as an alternative to the already existing synthetic commodity materials. The ring-opening polymerisation (ROP) of lactide, a bio-renewable resource produced by fermentation from sugar-roots and corn, has attracted the most attention, including ours.

Our alkaline earth complexes display excellent catalytic performances in the controlled immortal ring-opening polymerisation of “green” cyclic esters: lactide, gamma-butyrolactone, e-caprolactone, lactides, etc. These precatalysts rank amongst the best ones known to date for this catalysis, allowing efficient access to versatile biopolymers with controllable microstructures and predictable molecular weights.

Both heteroleptic charge-neutral and cationic alkaline earth complexes yield effective ROP catalysts, and thorough mechanistic studies (combining NMR, DFT, kinetics etc.) have enabled us to discriminate between the two families and ascertain the pertaining respective mechanisms.

SELECTED PUBLICATIONS FOR TOPIC 3

(1) Discrete divalent rare-earth cationic ROP catalysts: Ligand-dependent redox behavior and discrepancies with alkaline-earth analogues in a ligand-assisted activated monomer mechanism
B. Liu et al., Chem. Eur. J. 2013, 19, 3986. DOI: 10.1002/chem.201204340

(2) Heteroleptic silylamido phenolate complexes of calcium and the larger alkaline-earth metals: β-Agostic Si–H···Ae stabilization and activity in the ring-opening polymerization of L-lactide
B. Liu et al., Chem. Eur. J. 2012, 18, 6289. DOI: 10.1002/chem.201103666

(3) Discrete, solvent-free alkaline-earth metal cations: Metal···fluorine interactions and ROP catalytic activity
Y. Sarazin et al., J. Am. Chem. Soc. 2011, 133, 9069. DOI: 10.1021/ja2024977

(4) Bis(dimethylsilyl)amide complexes of the alkaline-earth metals stabilized by β-Si-H agostic interactions: Synthesis, characterization, and catalytic activity
Y. Sarazin et al., Organometallics 2010, 29, 6569. DOI: 10.1021/om100908q

We are very keen on exploring the organometallic chemistry on tetrelenes, tin(II) and lead(II), that remains underdeveloped to this day. Many discoveries await the imaginative synthetic chemists here!

Our chemistry in this field is developed in close collaboration with the group of Prof. Cristian Silvestru, at the University Babes-Bolyai in Cluj-Napoca, Romania.

Our initial interest in this area focused on understanding the principles of tin-mediated ring-opening polymerisation catalysis, since tin(II) is THE metal of choice for these reactions in industry. We have undertaken detailed mechanistic studies using our own tin(II) precatalysts in order to best mimic industrially relevant systems, and to understand what happens in batch-scale polymerisation reactors. We released several articles and patents that detail the accurate role of catalysts and co-catalysts in the controlled ring-opening polymerisation of lactide and related monomers.

More recently though, we have turned our attention to the more fundamental view of things, and have tried to pioneer the utilisation of new ligands in tin(II) and lead(II) chemistry. In particular, we are looking at how low-coordinate lead(II) alkoxides can be synthesised. We have also shown that bulky, and yet very simple ligands like boryloxides R₂BO^- and siloxides R₃SiO^- yield stable, two-coordinate lead(II) complexes never observed before !

Throughout all these exciting investigations, we were thrilled to be able to use unusual analytical tools like ¹¹⁹Sn and ²⁰⁷Pb multinuclear NMR spectroscopy as well as ¹¹⁹Sn Mossbauer spectroscopy. Combined to state-of-the-art theoretical computations, these tools have proved invaluable for the characterisation of the new tin(II) and lead(II) complexes and to assess accurately their role in catalysed processes!

​SELECTED PUBLICATIONS FOR TOPIC 4

(1) Lead(II) siloxides.
A.-A. Someșan et al., Chem. Eur. J. 2019, 25, 16236. DOI: 10.1002/chem.201904713

(2) Stable lead(II) boroxides.
A.-A. Someşan et al., Chem. Commun. 2018, 54, 5299. DOI: 10.1039/c8cc02459f

(3) Structurally characterized lead(II) alkoxides as potent ring-opening polymerization catalysts
L. Wang et al., Organometallics 2015, 34, 1321. DOI: 10.1021/acs.organomet.5b00052

(4) Structure vs ¹¹⁹Sn NMR chemical shift in three-coordinated tin(II) complexes: Experimental data and predictive DFT computations
L. Wang et al., Organometallics 2015, 34, 2139. DOI: 10.1021/om5007566

(5) Kinetic analysis of the immortal ring-opening polymerization of cyclic esters: A case study with tin(II) catalysts
L. Wang et al., Macromolecules 2014, 47, 2574. DOI: 10.1021/ma500124k