Archive for the ‘Bond slam’ Category

Two new types in the chemical bonding zoo: exo-bonds and hyper-bonds?

Wednesday, September 6th, 2017
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The chemical bond zoo is relatively small (the bond being a somewhat fuzzy concept, I am not sure there is an actual count of occupants). So when two new candidates come along, it is worth taking notice. I have previously noted the Chemical Bonds at the 21st Century-2017: CB2017 Aachen conference, where both were discussed.

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Chemical Bonds at the 21st Century – 2017: the Bond Slam.

Wednesday, August 2nd, 2017
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It is always interesting to observe conference experiments taking place. The traditional model involves travelling to a remote venue, staying in a hotel, selecting sessions to attend from a palette of parallel streams and then interweaving chatting to colleagues both old and new over coffee, lunch, dinner or excursions. Sometimes conferences occur in clusters, with satellite meetings breaking out in the vicinity, after a main conference has done the job of attracting delegates to the region. Here I bring to your attention one such experiment, the Bond Slam which is part of a satellite meeting in Aachen to be held September 2-4 2017 on the topic of Chemical Bonds at the 21st Century, following on from the WATOC 2017 congress in Munich Germany a few days earlier.

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First, hexacoordinate carbon – now pentacoordinate oxygen?

Saturday, March 25th, 2017
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The previous post demonstrated the simple iso-electronic progression from six-coordinate carbon to five coordinate nitrogen. Here, a further progression to oxygen is investigated computationally.

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First, hexacoordinate carbon – now pentacoordinate nitrogen?

Saturday, March 25th, 2017
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A few years back I followed a train of thought here which ended with hexacoordinate carbon, then a hypothesis rather than a demonstrated reality. That reality was recently confirmed via a crystal structure, DOI:10.5517/CCDC.CSD.CC1M71QM[1]. Here is a similar proposal for penta-coordinate nitrogen.

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References

  1. M. Malischewski, and K. Seppelt, "Crystal Structure Determination of the Pentagonal-Pyramidal Hexamethylbenzene Dication C6(CH3)62+", Angewandte Chemie International Edition, vol. 56, pp. 368-370, 2016. http://dx.doi.org/10.1002/anie.201608795

Na2He: a stable compound of helium and sodium at high pressure.

Saturday, February 11th, 2017
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On February 6th I was alerted to this intriguing article[1] by a phone call, made 55 minutes before the article embargo was due to be released. Gizmodo wanted to know if I could provide an (almost) instant quote. After a few days, this report of a stable compound of helium and sodium still seems impressive to me and I now impart a few more thoughts here.

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References

  1. X. Dong, A.R. Oganov, A.F. Goncharov, E. Stavrou, S. Lobanov, G. Saleh, G. Qian, Q. Zhu, C. Gatti, V.L. Deringer, R. Dronskowski, X. Zhou, V.B. Prakapenka, Z. Konôpková, I.A. Popov, A.I. Boldyrev, and H. Wang, "A stable compound of helium and sodium at high pressure", Nature Chemistry, vol. 9, pp. 440-445, 2017. http://dx.doi.org/10.1038/nchem.2716

Real hypervalency in a small molecule.

Sunday, February 21st, 2016
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Hypervalency is defined as a molecule that contains one or more main group elements formally bearing more than eight  electrons in their  valence shell. One example of a molecule so characterised was CLi6[1] where the description "“carbon can expand its octet of electrons to form this relatively stable molecule“ was used. Yet, in this latter case, the octet expansion is in fact an illusion, as indeed are many examples that are cited. The octet shell remains resolutely un-expanded. Here I will explore the tiny molecule CH3F2- where two extra electrons have been added to fluoromethane.

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References

  1. H. Kudo, "Observation of hypervalent CLi6 by Knudsen-effusion mass spectrometry", Nature, vol. 355, pp. 432-434, 1992. http://dx.doi.org/10.1038/355432a0