Guy Bertrand (chemist)

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Guy Bertrand, born on July 17, 1952, at Limoges is a chemistry professor at the University of California, San Diego. [1]

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Bertrand obtained his B.Sc. from the University of Montpellier in 1975 and his Ph.D. from the Paul Sabatier University, Toulouse, in 1979. He was a postdoctoral researcher at Sanofi Research, France, in 1981. [1]

The research interests of Bertrand and his co-workers lie mainly in the chemistry of with main group elements from group 13 to 16, at the border between organic, organometallic and inorganic chemistry; especially their use in stabilizing carbenes, nitrenes, phosphinidenes, radicals and biradicals, 1,3-dipoles, anti-aromatic heterocycles, and more. He has directed the synthesis of some original persistent carbenes, including bis(diisopropylamino)cyclopropenylidene, the first example of a carbene with all-carbon environment that is stable at room-temperature. [2]

Guy Bertrand is an honorific member or fellow of several scientific societies, such as the AAAS (2006), the French Academy of Sciences (2004), the European Academy of Sciences (2003), Academia Europaea (2002), and the recipient of various prizes and awards.

Scientific work

Questioning the current dogma is a design feature of Guy Bertrand's research program. He has made many important contributions to the chemistry of main group elements and new binding systems in inorganic, organometallic and organic chemistry. Throughout his career, he has isolated a variety of species [3] [4] [5] [6] [7] that were supposed to be only transitional intermediates, and are now powerful tools for chemists.

Its best-known contribution was the discovery in 1988 of the first stable carbene, a (phosphino)(silyl)carbene, [8] three years before Arduengo's report on a stable N-heterocyclic carbene. Guy Bertrand is at the origin of the chemistry of stable carbenes. Since then, he has made several revolutionary discoveries that have allowed us to better understand the stability of carbenes. He was the first to isolate cyclopropenylidenes, [2] mesoionic carbenes that cannot dimerize, resulting in a relaxation of steric requirements for their isolation [9] [10] More importantly, he discovered cyclic (alkyl) (amino) (amino) carbenes (CAACs), [11] including the recently published six-membered version. CAACs are even richer in electrons than NHCs and phosphines, but at the same time, due to the presence of a single pair of free electrons on nitrogen, CAACs are more accepting than NHCs. [12] The electronic properties of CAACs stabilize highly reactive species, including organic and major group radicals, as well as paramagnetic metal species, such as gold complexes (0), which were completely unknown. CAACs have also allowed the isolation of bis(copper)acetylide complexes, [13] which are key catalytic intermediates in the famous "Click Reaction", and which were supposed to be only transient species. He also used CAACs to prepare and isolate the first isoelectronic nucleophilic tricoordinated organoborane from amines. [14] [15] These recent developments appear paradoxical since they consist in using carbenes long considered as prototypic reactive intermediates to isolate otherwise unstable molecules. Among the large-scale applications already known of CAACs are their use as a ligand for transition metal catalysts. For example, in collaboration with Grubbs, Guy Bertrand has shown that ruthenium catalysts bearing a CAAC are extremely active in the ethenolysis of methyl oleate. [16] This is the first time that a series of metathesis catalysts have performed so well in cross-metathesis reactions using ethylene gas, with sufficient activity to make ethenolysis applicable to the industrial production of linear alpha-olefins (LAOs) and other olefinic end products from biomass.

Today, hundreds of academic and industrial groups use Guy Bertrand's CAACs and other carbenes in transition metal catalysis, [17] but also for other purposes. The most recent developments cover a wide range from nanoparticle stabilization to the antibacterial and anti-cancer properties of silver (I) and gold (I) complexes. A CAAC-copper complex even allows OLEDs to be used with a quantum efficiency close to 100% at high brightness. [18] The discovery of stable carbenes was a breakthrough for fundamental chemistry, a real paradigm shift, but its importance also comes, and perhaps more importantly, from applications. In his review article on "N-heterocyclic carbenes", a terminology that includes carbenes, Glorius et al. [19] wrote: "The discovery and development of N-heterocyclic carbenes is undoubtedly one of the greatest successes of recent chemical research", "N-heterocyclic carbenes are today among the most powerful tools in organic chemistry, with many applications in commercially important processes", "the meteoric rise of NHC is far from over".

Guy Bertrand's contribution is not limited to carbenes. Recent highlights include the isolation of the first stable nitrenes [20] and phosphinidenes. [21] He showed that the first can be used to transfer a nitrogen atom to organic fragments, a difficult task for nitrido complexes of transition metals. For the second, it has recently demonstrated that it mimics the behaviour of transition metals, just like carbenes. [22]

Honours and awards

He was awarded the CNRS silver medal in 1998. He is a member of the French Academy of Technology (2000), [23] the Academia Europaea (2002), [24] the European Academy of Sciences (2003), [24] the French Academy of Sciences (2004) [25] and the American Association for Advancement of Sciences (2006). [26] He was recently awarded the Sir Ronald Nyholm Medal from the SRC (2009), the Grand Prix Le Bel from the French Chemical Society (2010), the ACS Prize in Inorganic Chemistry (2014), the Sir Geoffrey Wilkinson Prize from the SRC (2016) and the Sacconi Medal from the Italian Chemical Society (2017). He is one of the associate editors of Chemical Reviews and a member of the editorial boards of several journals.

He is Chevalier of the Légion d'Honneur. [27]

Related Research Articles

In organic chemistry, a carbene is a molecule containing a neutral carbon atom with a valence of two and two unshared valence electrons. The general formula is R−:C−R' or R=C: where the R represents substituents or hydrogen atoms.

A transition metal carbene complex is an organometallic compound featuring a divalent carbon ligand, itself also called a carbene. Carbene complexes have been synthesized from most transition metals and f-block metals, using many different synthetic routes such as nucleophilic addition and alpha-hydrogen abstraction. The term carbene ligand is a formalism since many are not directly derived from carbenes and most are much less reactive than lone carbenes. Described often as =CR2, carbene ligands are intermediate between alkyls (−CR3) and carbynes (≡CR). Many different carbene-based reagents such as Tebbe's reagent are used in synthesis. They also feature in catalytic reactions, especially alkene metathesis, and are of value in both industrial heterogeneous and in homogeneous catalysis for laboratory- and industrial-scale preparation of fine chemicals.

<span class="mw-page-title-main">Persistent carbene</span> Type of carbene demonstrating particular stability

A persistent carbene is an organic molecule whose natural resonance structure has a carbon atom with incomplete octet, but does not exhibit the tremendous instability typically associated with such moieties. The best-known examples and by far largest subgroup are the N-heterocyclic carbenes (NHC), in which nitrogen atoms flank the formal carbene.

The triazol-5-ylidenes are a group of persistent carbenes which includes the 1,2,4-triazol-5-ylidene system and the 1,2,3-triazol-5-ylidene system. As opposed to the now ubiquitous NHC systems based on imidazole rings, these carbenes are structured from triazole rings. 1,2,4-triazol-5-ylidene can be thought of as an analog member of the NHC family, with an extra nitrogen in the ring, while 1,2,3-triazol-5-ylidene is better thought of as a mesoionic carbene (MIC). Both isomers of this group of carbenes benefit from enhanced stability, with certain examples exhibiting greater thermal stability, and others extended shelf life.

The Wanzlick equilibrium is a chemical equilibrium between a relatively stable carbene compound and its dimer. The equilibrium was proposed to apply to certain electron-rich alkenes, such as tetraminoethylenes, which have been called "carbene dimers." Such equilibria occur, but the mechanism does not proceed simply, but requires catalysts.

Carbene analogs in chemistry are carbenes with the carbon atom replaced by another chemical element. Just as regular carbenes they appear in chemical reactions as reactive intermediates and with special precautions they can be stabilized and isolated as chemical compounds. Carbenes have some practical utility in organic synthesis but carbene analogs are mostly laboratory curiosities only investigated in academia. Carbene analogs are known for elements of group 13, group 14, group 15 and group 16.

<span class="mw-page-title-main">Germylene</span> Class of germanium (II) compounds

Germylenes are a class of germanium(II) compounds with the general formula :GeR2. They are heavier carbene analogs. However, unlike carbenes, whose ground state can be either singlet or triplet depending on the substituents, germylenes have exclusively a singlet ground state. Unprotected carbene analogs, including germylenes, has a dimerization nature. Free germylenes can be isolated under the stabilization of steric hindrance or electron donation. The synthesis of first stable free dialkyl germylene was reported by Jutzi, et al in 1991.

<span class="mw-page-title-main">Phosphinidene</span> Type of compound

Phosphinidenes are low-valent phosphorus compounds analogous to carbenes and nitrenes, having the general structure RP. The "free" form of these compounds is conventionally described as having a singly-coordinated phosphorus atom containing only 6 electrons in its valence level. Most phosphinidenes are highly reactive and short-lived, thereby complicating empirical studies on their chemical properties. In the last few decades, several strategies have been employed to stabilize phosphinidenes, and researchers have developed a number of reagents and systems that can generate and transfer phosphinidenes as reactive intermediates in the synthesis of various organophosphorus compounds.

<span class="mw-page-title-main">PEPPSI</span> Group of chemical compounds

PEPPSI is an abbreviation for pyridine-enhanced precatalyst preparation stabilization and initiation. It refers to a family of commercially available palladium catalysts developed around 2005 by Prof. Michael G. Organ and co-workers at York University, which can accelerate various carbon-carbon and carbon-heteroatom bond forming cross-coupling reactions. In comparison to many alternative palladium catalysts, Pd-PEPPSI-type complexes are stable to air and moisture and are relatively easy to synthesize and handle.

In chemistry, mesoionic carbenes (MICs) are a type of reactive intermediate that are related to N-heterocyclic carbenes (NHCs); thus, MICs are also referred to as abnormal N-heterocyclic carbenes (aNHCs) or remote N-heterocyclic carbenes (rNHCs). Unlike simple NHCs, the canonical resonance structures of these carbenes are mesoionic: an MIC cannot be drawn without adding additional charges to some of the atoms.

Singlet fission is a spin-allowed process, unique to molecular photophysics, whereby one singlet excited state is converted into two triplet states. The phenomenon has been observed in molecular crystals, aggregates, disordered thin films, and covalently-linked dimers, where the chromophores are oriented such that the electronic coupling between singlet and the double triplet states is large. Being spin allowed, the process can occur very rapidly and out-compete radiative decay thereby producing two triplets with very high efficiency. The process is distinct from intersystem crossing, in that singlet fission does not involve a spin flip, but is mediated by two triplets coupled into an overall singlet. It has been proposed that singlet fission in organic photovoltaic devices could improve the photoconversion efficiencies.

<span class="mw-page-title-main">Cyclic alkyl amino carbenes</span> Family of chemical compounds

In chemistry, cyclic(alkyl)(amino)carbenes (CAACs) are a family of stable singlet carbene ligands developed by the research group of Guy Bertrand in 2005 at UC Riverside. In marked contrast with the popular N-heterocyclic carbenes (NHCs) which possess two "amino" substituents adjacent to the carbene center, CAACs possess one "amino" substituent and an sp3 carbon atom "alkyl". This specific configuration makes the CAACs very good σ-donors and π-acceptors when compared to NHCs. Moreover the reduced heteroatom stabilization of the carbene center in CAACs versus NHCs also gives rise to a smaller ΔEST.

<span class="mw-page-title-main">Borylene</span>

A borylene is the boron analogue of a carbene. The general structure is R-B: with R an organic moiety and B a boron atom with two unshared electrons. Borylenes are of academic interest in organoboron chemistry. A singlet ground state is predominant with boron having two vacant sp2 orbitals and one doubly occupied one. With just one additional substituent the boron is more electron deficient than the carbon atom in a carbene. For this reason stable borylenes are more uncommon than stable carbenes. Some borylenes such as boron monofluoride (BF) and boron monohydride (BH) the parent compound also known simply as borylene, have been detected in microwave spectroscopy and may exist in stars. Other borylenes exist as reactive intermediates and can only be inferred by chemical trapping.

<span class="mw-page-title-main">Phosphenium</span> Divalent cations of phosphorus

Phosphenium ions, not to be confused with phosphonium or phosphirenium, are divalent cations of phosphorus of the form [PR2]+. Phosphenium ions have long been proposed as reaction intermediates.

<span class="mw-page-title-main">Phosphasilene</span>

Phosphasilenes or silylidenephosphanes are a class of compounds with silicon-phosphorus double bonds. Since the electronegativity of phosphorus (2.1) is higher than that of silicon (1.9), the "Si=P" moiety of phosphasilene is polarized. The degree of polarization can be tuned by altering the coordination numbers of the Si and P centers, or by modifying the electronic properties of the substituents. The phosphasilene Si=P double bond is highly reactive, yet with the choice of proper substituents, it can be stabilized via donor-acceptor interaction or by steric congestion.

<span class="mw-page-title-main">Carbones</span> Class of molecules

Carbones are a class of molecules containing a carbon atom in the 1D excited state with a formal oxidation state of zero where all four valence electrons exist as unbonded lone pairs. These carbon-based compounds are of the formula CL2 where L is a strongly σ-donating ligand, typically a phosphine (carbodiphosphoranes) or a N-heterocyclic carbene/NHC (carbodicarbenes), that stabilises the central carbon atom through donor-acceptor bonds. Carbones possess high-energy orbitals with both σ- and π-symmetry, making them strong Lewis bases and strong π-backdonor substituents. Carbones possess high proton affinities and are strong nucleophiles which allows them to function as ligands in a variety of main group and transition metal complexes. Carbone-coordinated elements also exhibit a variety of different reactivities and catalyse various organic and main group reactions.  

<span class="mw-page-title-main">Organoberyllium chemistry</span> Organoberyllium Complex in Main Group Chemistry

Organoberyllium chemistry involves the synthesis and properties of organometallic compounds featuring the group 2 alkaline earth metal beryllium (Be). The area remains less developed relative to the chemistry of other main-group elements, because Be compounds are toxic and few applications have been found.

<span class="mw-page-title-main">Diphosphadiboretanes</span> Chemical compound

1,3-Diphospha-2,4-diboretanes, or B2P2, is a class of 4-member cyclic compounds of alternating boron and phosphorus atoms. They are often found as dimers during the synthesis of boraphosphenes (RB=PR'). Compounds can exhibit localized singlet diradical character (diradicaloid) between the boron atoms in the solution and solid state.

<span class="mw-page-title-main">Stable phosphorus radicals</span>

Stable and persistent phosphorus radicals are phosphorus-centred radicals that are isolable and can exist for at least short periods of time. Radicals consisting of main group elements are often very reactive and undergo uncontrollable reactions, notably dimerization and polymerization. The common strategies for stabilising these phosphorus radicals usually include the delocalisation of the unpaired electron over a pi system or nearby electronegative atoms, and kinetic stabilisation with bulky ligands. Stable and persistent phosphorus radicals can be classified into three categories: neutral, cationic, and anionic radicals. Each of these classes involve various sub-classes, with neutral phosphorus radicals being the most extensively studied. Phosphorus exists as one isotope 31P (I = 1/2) with large hyperfine couplings relative to other spin active nuclei, making phosphorus radicals particularly attractive for spin-labelling experiments.

A ketenyl anion contains a C=C=O allene-like functional group, similar to ketene, with a negative charge on either terminal carbon or oxygen atom, forming resonance structures by moving a lone pair of electrons on C-C-O bond. Ketenes have been sources for many organic compounds with its reactivity despite a challenge to isolate them as crystal. Precedent method to obtain this product has been at gas phase or at reactive intermediate, and synthesis of ketene is used be done in extreme conditions. Recently found stabilized ketenyl anions become easier to prepare compared to precedent synthetic procedure. A major feature about stabilized ketene is that it can be prepared from carbon monoxide (CO) reacting with main-group starting materials such as ylides, silylene, and phosphinidene to synthesize and isolate for further steps. As CO becomes a more common carbon source for various type of synthesis, this recent finding about stabilizing ketene with main-group elements opens a variety of synthetic routes to target desired products.

References

  1. 1 2 Guy Bertrand's faculty homepage at UC San Diego. Accessed on 2013-1-22.
  2. 1 2 V. Lavallo, Y. Canac, B. Donnadieu, W. W. Schoeller, G. Bertrand, « Cyclopropenylidenes: From Interstellar Space to an isolated Derivative in the Laboratory », Science, 2006, 312, p. 722–724
  3. ↑ G. Bertrand, R. Nakano, R. Jazzar, « A Crystalline Mono-Substituted Carbene », Nature Chem., 2018, 10, p. 1196-1200
  4. ↑ D. Scheschkewitz, H. Amii, H. Gornitzka, W.W. Schoeller, D. Bourissou, G. Bertrand, « Singlet diradicals: from transition states to crystalline compounds », Science, 2002, 295, p. 1880–1881
  5. ↑ S. Sole, H. Gornitzka, W.W. Schoeller, D. Bourissou, G. Bertrand, « (Amino)(aryl)carbenes : stable singlet carbenes featuring a spectator substituent », Science, 2001, 292, p. 1901-1903
  6. ↑ D. Bourissou, O. Guerret, F. Gabbaï, G. Bertrand, « Stable carbenes », Chem. Rev., 2000, 100, p. 39-91
  7. ↑ Y. Canac, D. Bourissou, A. Baceiredo, H. Gornitzka, W. W. Schoeller, G. Bertrand,, « Isolation of a benzene valence isomer with one-electron phosphorus-phosphorus bonds », Science, 1998, 279, p. 2080–2082
  8. ↑ A. Igau, H. Grutzmacher, A. Baceiredo, G. Bertrand, «  Analogous a, a' bis carbenoid triply bonded species : synthesis of a stable l 3-phosphinocarbene _l 5-phosphaacetylene », J. Am. Chem. Soc., 1988, 110, p. 6463–6466
  9. ↑ G. Guisado-Barrios, J. Bouffard, B. Donnadieu, G. Bertrand, « Crystalline 1H-1,2,3-Triazol-5-ylidenes: New Stable Mesoionic Carbenes (MICs) », Angew. Chem. Int. Ed., 2010, 49, p. 4759-4762
  10. ↑ E. Aldeco-Perez, A. J. Rosenthal, B. Donnadieu, P. Parameswaran, G. Frenking, G. Bertrand, « Isolation of a C-5-Deprotonated Imidazolium, a Crystalline “Abnormal” N-Heterocyclic Carbene », Science, 2009, 326, p. 556–559
  11. ↑ V. Lavallo, Y. Canac, A. Dehope, B. Donnadieu, G. Bertrand, « A Rigid Cyclic (Alkyl)(amino)carbene Ligand Leads to Isolation of Low-Coordinate Transition-Metal Complexes », Angew. Chem. Int. Ed., 2005, 44, p. 7236–7239
  12. ↑ M. Melaimi, R. Jazzar, M. Soleilhavoup, G. Bertrand,, « Cyclic (Alkyl)(Amino)Carbenes (CAACs): Recent developments », Angew. Chem. Int. Ed., 2017, 56, p. 10046-10068
  13. ↑ L. Jin, D. R. Tolentino, M. Melaimi, G. Bertrand, « Isolation of Bis(copper) Key Intermediates in Cu-Catalyzed Azide–Alkyne “Click Reaction.” », Sci. Adv., 2015, 1, e1500304
  14. ↑ F. Dahcheh, D. Martin, D. W. Stephan, G. Bertrand, « Synthesis and Reactivity of a CAAC-Aminoborylene Adduct: A Hetero-Allene or an Organoboron Isoelectronic with Singlet Carbenes? », Angew. Chem. Int. Ed., 2014, 53, p. 13159
  15. ↑ R. Kinjo, B. Donnadieu, M. Ali Celik, G. Frenking, G. Bertrand, « Synthesis and Characterization of a Neutral Tricoordinate Organoboron Isoelectronic with Amines », Science, 2011, 333, p. 610–613
  16. ↑ V. M. Marx, A. H. Sullivan, M. Melaimi, S. C. Virgil, B. K. Keitz, D. S. Weinberger, G. Bertrand, R. H. Grubbs, « Cyclic Alkyl Amino Carbene (CAAC) Ruthenium Complexes as Remarkably Active Catalysts for Ethenolysis », Angew. Chem. Int. Ed., 2015, 54, p. 1919
  17. ↑ E. A. Romero, T. Zhao, R. Nakano, X. Hu, Y. Wu, R. Jazzar, G. Bertrand, « Tandem Copper Hydride - Lewis Pair Catalyzed Reduction of Carbon Dioxide into Formate with Dihydrogen », Nature Catal., 2018, 1, p. 743-747
  18. ↑ R. Hamze, J. L. Peltier, D. Sylvinson1, M. Jung, J. Cardenas, R. Haiges, M. Soleilhavoup2, R. Jazzar, P. I. Djurovich, G. Bertrand, M. E. Thompson, « Eliminating nonradiative decay in Cu(I) emitters: >99% quantum efficiency and microsecond lifetime », Science, 2019, 363, p. 601-609
  19. ↑ Hopkinson, M. N.; Richter, C.; Schedler, M.; Glorius F., « An overview of N-heterocyclic carbenes », Nature, 2014, 510, p. 485-496 (DOI DOI: 10.1038/nature13384)
  20. ↑ F. Dielmann, O. Back, M. Henry-Ellinger, P. Jerabek, G. Frenking, G. Bertrand, « A Crystalline Singlet Phosphinonitrene: a Nitrogen Atom Transfer Agent », Science, 2012, 337, p. 1526–1528
  21. ↑ L. Liu, D. A. Ruiz, D. Munz, G. Bertrand, « A Room Temperature Stable Singlet Phosphinidene », Chem, 2016, 1, p. 147–153
  22. ↑ G. D. Frey, V. Lavallo, B. Donnadieu, W. W. Schoeller, G. Bertrand, « Facile Splitting of Hydrogen and Ammonia by Nucleophilic Activation at a Single Carbon Center », Science, 2007, 316, p. 439–441
  23. ↑ "Académie des technologies". Archived from the original on 2019-04-23. Retrieved 2019-08-07.
  24. 1 2 "Academia europaea".
  25. ↑ "Académie des sciences".
  26. ↑ "American Association for advancement of science".
  27. ↑ "Légion d'honneur". Archived from the original on 2019-04-23. Retrieved 2019-08-07.


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