Aromaticity in Boron Clusters Survives Radical Structural Changes

Whereas the aromaticity of closo boranes is widely accepted, less is known about the aromaticity of nido boranes. This work carried out by Prof. Francesc Teixidor, Prof. Clara Viñas, and Dr. Ines Bennour of the Institute of Materials Science of Barcelona (ICMAB-CSIC), Prof. Jordi Poater at the University of Barcelona (previous DiMoCat member) and Sílvia Escayola and Prof. Miquel Solà members of the DiMoCat group of the Institute of Computational Chemistry and Catalysis of the University of Girona, experimentally shows that deboronation of m-C2B9H12 is a difficult task, whereas deboranation of o-C2B9H12 is quite easy. Moreover, it is widely known that o-C2B10H12 isomerizes to m-C2B10H12 upon heating at 400 ºC. These two facts indicate that m-C2B10H12 is more stable than o-C2B10H12. To find a reason for the different stability of these two isomers, authors have analyzed the thermodynamic stability and aromaticity of these closo carboranes and their nido counterparts. Results show that the higher thermodynamic stability of m-C2B10H12 is not related to aromaticity differences but to the location of the C atoms in the carborane structure. It is also demonstrated that the aromaticity observed in closo boranes and carboranes is also present in their nido counterparts and, consequently, authors conclude that aromaticity in boron clusters survives radical structural changes. Further, sandwich metallocenes (e.g. ferrocene) and sandwich metallacarboranes (e.g. [Co(C2B9H11)2]) have traditionally been considered similar. In this work, it is shown that they are not. Metallacarboranes display global aromaticity, whereas metallocenes present local aromaticity in the ligands. Remarkable and unique is the double probe given by 1H- and 11B-NMR tracing the reciprocally antipodal endocyclic open face Hec and B1. These magnetic studies have permitted to correlate both nuclei and relate them to a diatropic current in the plane at the middle of the nido-[C2B9H12]. This observation is the first and unique data that proves experimentally the existence of diatropic currents, thence aromaticity, in nido clusters and is comparable to the existence of diatropic currents in planar aromatic compounds.

 

 

Poater, J.; Viñas, C.; Bennour, I.; Escayola, S.; Solà*, M.; Teixidor*, F. Too Persistent to Give Up: Aromaticity in Boron Clusters Survives Radical Structural Changes. J. Am. Chem. Soc., 2020, DOI: 10.1021/jacs.0c02228

Financial support: This work has been supported by the Ministerio de Economía y Competitividad (MINECO) of Spain (Projects CTQ2017-85341-P, CTQ2016-77558-R, and MDM-2017-0767) and the Generalitat de Catalunya (projects 2017SGR39 and 2017SGR348). Excellent service by the Supercomputer center of the Consorci de Serveis Universitaris de Catalunya (CSUC) is gratefully acknowledged.

Two ICREA Acadèmia awards at IQCC: Anna Company and Albert Poater

ICREA announced the list of winners of the ICREA Acadèmia awards 2019, among which are three (!!!) names from the University of Girona: Sebastià Puig (Engineering), Anna Company and Albert Poater (both IQCC and Chemistry). Albert Poater belongs to DIMOCAT group.

 

                                             

Unprecedented Selectivity of Ruthenium Iodide Benzylidenes in Olefin Metathesis Reactions

Olefin metathesis seems to be a complex chemical reaction, but if we say that leads to the formation of polymers, i.e. plastics, it is really simple and it is valid in any item that currently we have in our hands. This field of olefin metathesis is mature, after the Nobel Prize in 2005 of Chauvin, Schrock and Grubbs, but still here with two simple modifications we have been able to get novel catalysts that lead to amazing selectivity. In collaboration with the Ben-Gurion University of the Negev, the IQCC team from DIMOCAT led by Albert Poater shows that cis-diiodo sulfur chelated ruthenium benzylidenes do not react with strained cycloalkenes and internal olefins, but can effectively catalyze metathesis reactions of terminal dienes. Surprisingly, internal olefins may partake in olefin metathesis reactions once the ruthenium methylidene intermediate is generated. This unexpected behavior allows the facile formation of strained cis-cyclooctene by the RCM reaction of 1,9-undecadiene. Once in silico calculations confirmed the promising different behavior of those novel catalysts, the impressively latent catalyst was activated experimentally by addition of an external chloride source, unveiling a novel method for controlled polymerization of DCPD.

B. Nechmad, R. Phatake, E. Ivry, A. Poater, N. G. Lemcoff; “Unprecedented Selectivity of Sulfur Chelated Ruthenium Iodide Benzylidenes in Olefin Metathesis Reactions”; Angew. Chem. Int. Ed. 2020, accepted. DOI: 10.1002/anie.201914667

 

Amazing combination of factors transforms chemistry into green chemistry

In search of green or sustainable chemistry there are different objectives to achieve, and already achieve successfully one already represents a step forward to improve the world that surrounds us. Here, in this collaborative work between the experimental team of the University of Normandy (France) led by Prof. Jean Luc Renaud, and from Girona, Dr. Albert Poater the computational complementary part, has been able to achieve not only find a catalyst capable of fixing CO2, but to find out one that is not based on noble metals, expensive, and of high toxicity, and furthermore, dealing with water as a solvent. An iron, most abundant metal catalyst of the Earth’s layer has been employed.  Overall, a highly efficient, stable, phosphine-free, and easy-to-synthesize iron catalyst system for the reduction of CO2, hydrogenocarbonate, and carbonate in pure water is reported.

Coufourier, Q. Gaignard-Gaillard, J.-F. Lohier, A. Poater, S. Gaillard, J.-L. Renaud; “Hydrogenation of CO2, Hydrogenocarbonate, and Carbonate to Formate in Water using Phosphine Free Bifunctional Iron Complexes”; ACS Catal. 2020, 10, 2108-2116. DOI: 10.1021/acscatal.9b04340

Two new PhD students in the DiMoCat group

We have recently incorporated two new PhD students in our group with two cotutelle agreements.

First, Daniel Eduardo Trujillo that will perform a theoretical study of the electronic structure and reaction mechanisms of reactions of multiple-bound boron compounds that can activate C-C and C-H bonds. Daniel will be supervised by J. Oscar C. Jimenez-Halla and Gerardo Gonzalez in the University of Guanajauto (Mexico) and Miquel Solà in the University of Girona.

A photo of Daniel E. Trujillo

Second, Dandan Chen that will be working in the study of aromatic species with special emphasis in metalloaromatic species in excited states. Dandan will be supervised by Jun Zhu in Xiamen University (China) and Miquel Solà in the University of Girona.


A photo of Dandan Chen

We wish Daniel and Dandan a great success with their PhD research!

Two recent DiMoCat works highlighted by ChemistryWorld

ChemistryWorld has recently highlighted two works of our group:

The jellium model assumes a uniform distribution of positive charge corresponding to the cluster atomic nuclei and their innermost electrons in which the interacting valence electrons move. The energy levels of valence electrons for such a model are 1S21P61D102S21F142P61G182D103S2…, where S, P, D, F, and G letters denote the angular momentum and numbers 1, 2, 3 indicate the radial nodes. The abundance found in experimental mass spectra of alkali, alkaline earth metals, and gold clusters of 2, 8, 18, 20, 34, 40… atoms are justified taken into account that these numbers correspond to closed-shell electronic structures in the jellium model. We have proven that if the last energy level of valence electrons for the jellium model is half-filled with same-spin electrons, the system has also an aromatic character that provides extra stability. This situation is reached for the magic numbers of valence electrons of 1 (S =1/2), 5 (S = 3/2), 13 (S = 5/2), 19 (S = 1/2), 27 (S = 7/2), 37 (S = 3/2), 49 (S = 9/2)… This new set of magic numbers may become a powerful tool for researchers who work in the quest for stable single high-spin molecules for their use as single-molecule based magnets. The paper has been published in Chem. Commun. and can be found in the following link Chem. Commun., 55 (2019) 5559-5562.

In this recent Chem. Commun. paper, we have proved that C18 (a cycle of 18 carbon atoms connected with alternating single and triple bonds) it is an electron acceptor of similar characteristics as C60. C18  when coupled with a range of donor molecules can readily accept electrons. Electron acceptors are important components in molecular electronic devices and solar cells, and, therefore, C18 is added to the list of organic electron acceptors that can be potentially useful in photovoltaics.

Visit of Kamila Pruszkowska

Kamila Pruszkowska is a PhD student supervised by Prof. Michal Cyranski in the University of Warsaw . She has been working in our group for the last six weeks working in the study of the 1,2-bis(4-methylbenzoylvinylamino)ethane and Ni (II) 1,3-bis(4-methylbenzoylvinylamino)propane Ni(II) complexes coordinated to pyridine, 4-dimethylaminopyridine, 4-metoxypyridine, N-methyloimidazole, and thiazole ligands. She has been financed by an HPC-Europa3 fellowship and during her stay in our group she has been supervised by Dr. Olga A. Stasyuk and Dr. Miquel Solà. We are very happy to have had her in our group! We hope she has enjoyed her stay!

Kamila in the center with Olga and Miquel

3 researchers from DIMOCAT among the 11 best researchers list of Universitat de Girona

Alexander Voityuk, investigador de la UdG

The work carried by DIMOCAT research group of the Institut de Química Computacional i Catàlisi (IQCC) and Universitat de Girona (UdG) has been recognized recently with the inclusion of three researchers of DIMOCAT, Prof. Dr. Miquel Solà, Prof. Dr. Alexander Voityuk and Dr. Albert Poater, in the classification by Prof. Dr. John P. A. Ioannidis and coworkers (A standardized citation metrics author database annotated for scientific field).

https://journals.plos.org/plosbiology/article/file?id=10.1371/journal.pbio.3000384&type=printable

These 3 researchers have been included, apart from other 8 scientists from the same university, UdG, actually overall 6 from IQCC. This classification has created a publicly available database of 100,000 top world scientists, active or retired yet, that provides standardized information on citations, h-index, coauthorship-adjusted hm-index, citations to papers in different authorship positions, and a composite indicator. Separate data are shown for career-long and single-year impact. Metrics with and without self-citations and ratio of citations to citing papers are given. Scientists
are classified into 22 scientific fields and 176 subfields. Field- and subfield-specific percentiles are also provided for all scientists who have published at least five papers. Career-long data are updated to end of 2017 and to end of 2018 for comparison.

HPC-Europa3 – DiMoCat host

This week three visitors of our group have been awarded with an HPC-Europa3 Program grant. In particular, DiMoCat will be the host of the following three visitors:

Massimo Christian D’Alterio from the University of Naples Federico II, Naples (Italy)

Gerard Pareras Niell from the  University College Cork, Cork (Ireland)

Kamila Pruszkowska from the University of Warsaw, Warsaw (Poland)

We wish all our visitors a good stay in Girona!

ChemistryWorld and Chem. Commun. Inside Front Cover highlighting the discovery of open-shell jellium aromaticity in metal clusters

Jordi Poater from the Universitat de Barcelona (ex-DiMoCat member) together with the DiMoCat member Miquel Solà have derived a new rule for the open-shell jellium aromaticity. Some years ago, the same two authors demonstrated that spherical compounds having a same-spin half-filled last energy level with the rest of the levels being full filled are aromatic. They showed that this situation is reached for a number of electrons equal to 2N2 + 2N + 1 with S = N + ½ and proved that, among others, C60-1 with S = 11/2 or C80-5 species with S = 13/2 are aromatic fullerenes.

Now, they have extended this finding to metal clusters. The jellium model assumes a uniform distribution of positive charge corresponding to the cluster atomic nuclei and their innermost electrons in which the interacting valence electrons move. The energy levels of valence electrons for such a model are 1S21P61D102S21F142P61G182D103S2…, where S, P, D, F, and G letters denote the angular momentum and numbers 1, 2, 3 indicate the radial nodes. The abundance found in experimental mass spectra of alkali, alkaline earth metals, and gold clusters of 2, 8, 18, 20, 34, 40… atoms are justified taken into account that these numbers correspond to closed-shell electronic structures in the jellium model. Poater and Solà have proven that if the last energy level of valence electrons for the jellium model is half-filled with same-spin electrons, the system has also some extra stability and has aromatic character. This situation is reached for the magic numbers of valence electrons of 1 (S =1/2), 5 (S = 3/2), 13 (S = 5/2), 19 (S = 1/2), 27 (S = 7/2), 37 (S = 3/2), 49 (S = 9/2)… This new set of magic numbers may become a powerful tool for researchers who work in the quest for stable single high-spin molecules for their use as single-molecule based magnets.

The paper has been published in Chem. Commun. and can be found in the following link Chem. Commun., 55 (2019) 5559-5562. Moreover, the paper has been highlighted by Chemistry World and Chem. Commun. has dedicated the inside back cover of the issue 39 of volume 55 to this work: