Catenated atoms and groups.

Chemists are as fond of records as any, although I doubt you will find many chemical ones in the Guinness world records list. Polytriangulanes chase how many cyclopropyl 3-rings can be joined via a vertex. Steve Bachrach on his blog reports some recent work by Peter Schreiner and colleagues[cite]10.1021/acs.jctc.6b00669[/cite] and the record for catenation of such rings appears to be 15. This led me to think about some other common atoms and groups. Here I have searched for crystal structures only; there may be examples of course for which no such data has been reported.

  1. For the halogens F and Cl it is 3. 
  2. But for Br, believe it or not it reaches the heady value of 24, doi: 10.5517/CC14K0PD[cite]10.5517/CC14K0PD[/cite]
  3. For iodine it is effectively infinite, as noted in my earlier post.
  4. For oxygen it is 3; there are none with four consecutive oxygens.
  5. For sulfur, a ring of twelve is known[cite]10.1002/zaac.19814760520[/cite] and for Se ~11[cite]10.1021/ic00325a026[/cite]
  6. For nitrogen it may surprise to learn it reaches 6 if the connecting bonds are all single. A typical example can be seen at doi: 10.5517/CCZCR35[cite]10.5517/CCZCR35[/cite] It reaches 10 if any kind of  N-N bond is allowed. doi: 10.5517/CCYVNZD
  7. For phosphorus, 16 is not uncommon 10.5517/CC1JWTQY [cite]10.5517/CC1JWTQY[/cite] but the record may be 21.
  8. The alkyne group C≡C, reaches 10 (20 carbon atoms), doi: 10.5517/CCSGR98 [cite]10.5517/CCSGR98[/cite]
  9. The carbonyl group (C=O) can form a ring of six such groups 10.5517/CC9JR6R[cite]10.5517/CC9JR6R[/cite]

Such records are probably very uncompetitive; I doubt any researchers set out to extend the count. Most of the above are probably simply unexpected discoveries. My favourite is the bromine example; this element so often surprises.

This entry was posted on Thursday, October 13th, 2016 at 11:37 am and is filed under crystal_structure_mining. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.

3 Responses to “Catenated atoms and groups.”

  1. Cina Foroutan-Nejad says:
    October 14, 2016 at 9:44 am

    A fresh chlorine octamer: 10.1002/anie.201604348

    Reply
  2. Henry Rzepa says:
    October 16, 2016 at 10:02 am

    The 3D structure for this [Cl8]2- species can be seen at doi: 10.5517/ccdc.csd.cc1kwp7c

    Reply
  3. Henry Rzepa says:
    October 16, 2016 at 10:04 am

    Almost as soon as I asserted that the record for a string of P atoms joined to each other was 21, an example with an infinite such chain is found. It is part of a double helix, see this post.

    Reply

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