{"id":16819,"date":"2016-09-19T11:02:37","date_gmt":"2016-09-19T10:02:37","guid":{"rendered":"http:\/\/www.ch.imperial.ac.uk\/rzepa\/blog\/?p=16819"},"modified":"2016-09-19T11:02:37","modified_gmt":"2016-09-19T10:02:37","slug":"whats-in-a-name-stabilised-nitrenes","status":"publish","type":"post","link":"https:\/\/www.rzepa.net\/blog\/?p=16819","title":{"rendered":"What\u2019s in a name? Stabilised “nitrenes”."},"content":{"rendered":"
\n

I previously explored<\/a> stabilized “carbenes” with the formal structures (R2<\/sub>N)2<\/sub>C:, concluding that perhaps the alternative ionic representation R2<\/sub>N+<\/sup>=C–<\/sup>NR2<\/sub>\u00a0might reflect their structures better. Here I take a broader look at the “carbene” landscape before asking the question “what about nitrenes?”<\/p>\n

\"carbenes\"<\/a><\/p>\n

The top row shows the compounds for which no crystal structure could be found.\u2021<\/sup> This includes the traditional carbon-substituted unstabilized carbenes, as well as those substituted with either group 4A or 6A elements (Si, S, etc). Isolated hits were<\/strong>\u00a0however found as follows for other combinations (all interesting, but I do not discuss them here).<\/p>\n

    \n
  1. R2<\/sub>N-C-CR3\u00a0<\/sub>[1]<\/a><\/span>,[2]<\/a><\/span>,[3]<\/a><\/span>,[4]<\/a><\/span>,[5]<\/a><\/span>,[6]<\/a><\/span><\/li>\n
  2. R2<\/sub>P-C-Si [7]<\/a><\/span>,[8]<\/a><\/span><\/li>\n
  3. R2<\/sub>P-C-PR2<\/sub> [9]<\/a><\/span>,[10]<\/a><\/span><\/li>\n
  4. R2<\/sub>N-C-OR [11]<\/a><\/span><\/li>\n
  5. R2<\/sub>N-C-SR [12]<\/a><\/span><\/li>\n<\/ol>\n

    At this point I turned to nitrenes<\/a>. As with unstabilised carbenes, the nitrogen is\u00a0described as having one covalent bond, one unshared spin-paired lone pair of electrons and two further unpaired electrons to give a total valence shell count of six (and in fact a triplet spin state). Are there any examples? Just one, formally corresponding to\u00a0R2<\/sub>P-N (DEGSEP[13]<\/a><\/span>). To explore what the nature of the single P-N bond is, I did a search for the P-N bond lengths of all P-N compounds in the CSD (of any bond type). The distribution shows ~1.48\u00c5 as the shortest and ~1.8\u00c5 as the longest.There is no sign of a multimodal distribution indicating partitioning into e.g.<\/em> single, double or triple bonds.<\/p>\n

    \"p-n-distances\"<\/p>\n

    So what about our nitrene? The P-N bond is 1.456\u00c5, which is very much at the short end of the spectrum above, and so pretty far from the formal simple definition of a nitrene given above. So now for a\u00a0\u03c9B97XD\/Def2-TZVPP calculation of the singlet wavefunction[14]<\/a><\/span> (the triplet state is 22 kcal\/mol higher in energy[15]<\/a><\/span>) for a model compound with calculated CN distance 1.493\u00c5 and from which an ELF-based localisation and integration of the electron basins can be derived. The total basin integration for the N can be taken as 7.77e (close to the octet) if basins 15 and 16 are assumed to be shared (covalent) and this gives the P-N bond double bond character. If basins 15 and 16 are not included (and taken as localised just on the P), the N has 5.81e and an associated single bond.\u00a0<\/p>\n

    \"nitrene1\"<\/p>\n

    A search of the CSD specifying P\u2261N as the search query returns lengths in the range 1.47-1.56\u00c5, which our example certainly conforms to. So perhaps we can tentatively conclude that the only example thus far reported of a crystalline nitrene in fact sustains a very short bond to the nitrogen. It could be considered as the N having a filled octet in its valence shell, and certainly a bond order higher than one, if not actually triple.<\/p>\n

    \n

    \u2021<\/sup>For the search query, see [16]<\/a><\/span><\/p>\n

    References<\/h2>\n
    1. Marchenko, Anatoliy., Koidan, Heorgyi., Hurieva, Anastasiya., Kurpiieva, Olena., Vlasenko, Yurii., Kostyuk, Aleksandr., Tubaro, Cristina., Lenarda, Anna., Biffis, Andrea., and Graiff, Claudia., \"CCDC 997216: Experimental Crystal Structure Determination\", 2014. https:\/\/doi.org\/10.5517\/cc12gp8h<\/a>\n\n<\/li>\n
    2. A. Marchenko, H. Koidan, A. Hurieva, O. Kurpiieva, Y. Vlasenko, A. Kostyuk, C. Tubaro, A. Lenarda, A. Biffis, and C. Graiff, \"N-phosphanyl-imidazolin-2-ylidenes: Novel stable carbenes as bidentate ligands for late transition metals\", Journal of Organometallic Chemistry<\/i>, vol. 771, pp. 14-23, 2014. https:\/\/doi.org\/10.1016\/j.jorganchem.2014.05.036<\/a>\n\n<\/li>\n
    3. Lavallo, V.., Mafhouz, J.., Canac, Y.., Donnadieu, B.., Schoeller, W.W.., and Bertrand, G.., \"CCDC 236934: Experimental Crystal Structure Determination\", 2004. https:\/\/doi.org\/10.5517\/cc7yk1r<\/a>\n\n<\/li>\n
    4. V. Lavallo, J. Mafhouz, Y. Canac, B. Donnadieu, W.W. Schoeller, and G. Bertrand, \"Synthesis, Reactivity, and Ligand Properties of a Stable Alkyl Carbene\", Journal of the American Chemical Society<\/i>, vol. 126, pp. 8670-8671, 2004. https:\/\/doi.org\/10.1021\/ja047503f<\/a>\n\n<\/li>\n
    5. Lavallo, V.., Frey, G.D.., Kousar, S.., Donnadieu, B.., and Bertrand, G.., \"CCDC 651272: Experimental Crystal Structure Determination\", 2008. https:\/\/doi.org\/10.5517\/ccpvpsz<\/a>\n\n<\/li>\n
    6. V. Lavallo, G.D. Frey, S. Kousar, B. Donnadieu, and G. Bertrand, \"Allene formation by gold catalyzed cross-coupling of masked carbenes and vinylidenes\", Proceedings of the National Academy of Sciences<\/i>, vol. 104, pp. 13569-13573, 2007. https:\/\/doi.org\/10.1073\/pnas.0705809104<\/a>\n\n<\/li>\n
    7. Marsh, R.E.., and Clemente, D.A.., \"CCDC 625624: Experimental Crystal Structure Determination\", 2008. https:\/\/doi.org\/10.5517\/ccp00f3<\/a>\n\n<\/li>\n
    8. R.E. Marsh, and D.A. Clemente, \"A survey of crystal structures published in the Journal of the American Chemical Society\", Inorganica Chimica Acta<\/i>, vol. 360, pp. 4017-4024, 2007. https:\/\/doi.org\/10.1016\/j.ica.2007.02.050<\/a>\n\n<\/li>\n
    9. Martin, D.., Baceiredo, A.., Gornitzka, H.., Schoeller, W.W.., and Bertrand, G.., \"CCDC 252551: Experimental Crystal Structure Determination\", 2005. https:\/\/doi.org\/10.5517\/cc8gst9<\/a>\n\n<\/li>\n
    10. D. Martin, A. Baceiredo, H. Gornitzka, W.W. Schoeller, and G. Bertrand, \"A Stable P\u2010Heterocyclic Carbene\", Angewandte Chemie International Edition<\/i>, vol. 44, pp. 1700-1703, 2005. https:\/\/doi.org\/10.1002\/anie.200462239<\/a>\n\n<\/li>\n
    11. R.W. Alder, C.P. Butts, and A.G. Orpen, \"Stable Aminooxy- and Aminothiocarbenes\", Journal of the American Chemical Society<\/i>, vol. 120, pp. 11526-11527, 1998. https:\/\/doi.org\/10.1021\/ja9819312<\/a>\n\n<\/li>\n
    12. A.J. Arduengo, J.R. Goerlich, and W.J. Marshall, \"A Stable Thiazol\u20102\u2010ylidene and Its Dimer\", Liebigs Annalen<\/i>, vol. 1997, pp. 365-374, 1997. https:\/\/doi.org\/10.1002\/jlac.199719970213<\/a>\n\n<\/li>\n
    13. Dielmann, F.., Back, O.., Henry-Ellinger, M.., Jerabek, P.., Frenking, G.., and Bertrand, G.., \"CCDC 884586: Experimental Crystal Structure Determination\", 2013. https:\/\/doi.org\/10.5517\/ccyph14<\/a>\n\n<\/li>\n
    14. H. Rzepa, \"DEGSEP\", 2016. https:\/\/doi.org\/10.14469\/hpc\/1625<\/a>\n\n<\/li>\n
    15. H. Rzepa, \"DEGSEP triplet\", 2016. https:\/\/doi.org\/10.14469\/hpc\/1626<\/a>\n\n<\/li>\n
    16. H. Rzepa, \"CSD Search query for carbenes\", 2016. https:\/\/doi.org\/10.14469\/hpc\/1624<\/a>\n\n<\/li>\n<\/ol>\n\n<\/div> ","protected":false},"excerpt":{"rendered":"

      I previously explored stabilized “carbenes” with the formal structures (R2N)2C:, concluding that perhaps the alternative ionic representation R2N+=C–NR2\u00a0might reflect their structures better. Here I take a broader look at the “carbene” landscape before asking the question “what about nitrenes?” The top row shows the compounds for which no crystal structure could be found.\u2021 This includes […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"jetpack_post_was_ever_published":false,"_jetpack_newsletter_access":"","_jetpack_dont_email_post_to_subs":true,"_jetpack_newsletter_tier_id":0,"_jetpack_memberships_contains_paywalled_content":false,"_jetpack_memberships_contains_paid_content":false,"footnotes":"","jetpack_publicize_message":"","jetpack_publicize_feature_enabled":true,"jetpack_social_post_already_shared":true,"jetpack_social_options":{"image_generator_settings":{"template":"highway","default_image_id":0,"font":"","enabled":false},"version":2}},"categories":[1754],"tags":[],"class_list":["post-16819","post","type-post","status-publish","format-standard","hentry","category-crystal_structure_mining"],"jetpack_publicize_connections":[],"jetpack_featured_media_url":"","jetpack_sharing_enabled":true,"jetpack_shortlink":"https:\/\/wp.me\/p1gPyz-4nh","jetpack_likes_enabled":true,"_links":{"self":[{"href":"https:\/\/www.rzepa.net\/blog\/index.php?rest_route=\/wp\/v2\/posts\/16819","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.rzepa.net\/blog\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.rzepa.net\/blog\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.rzepa.net\/blog\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.rzepa.net\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=16819"}],"version-history":[{"count":0,"href":"https:\/\/www.rzepa.net\/blog\/index.php?rest_route=\/wp\/v2\/posts\/16819\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.rzepa.net\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=16819"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.rzepa.net\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=16819"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.rzepa.net\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=16819"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}