{"id":13158,"date":"2014-12-07T10:28:22","date_gmt":"2014-12-07T10:28:22","guid":{"rendered":"http:\/\/www.ch.imperial.ac.uk\/rzepa\/blog\/?p=13158"},"modified":"2014-12-07T10:28:22","modified_gmt":"2014-12-07T10:28:22","slug":"halogen-bonds-4-the-strongest-halogen-bond","status":"publish","type":"post","link":"https:\/\/www.rzepa.net\/blog\/?p=13158","title":{"rendered":"Halogen bonds 4: The strongest (?) halogen bond."},"content":{"rendered":"
\n

Continuing my hunt<\/a>, here is a candidate for a strong(est?) halogen bond, this time between Se and I.[1]<\/a><\/span>.
\n\"OXSELI\"<\/a>
\nThe features of interest include:<\/p>\n

    \n
  1. The six-membered ring is in the chair conformation.<\/li>\n
  2. The (relatively enormous) I…I substituent is axial<\/strong>!<\/li>\n
  3. It is attached to the Se rather than the O.<\/li>\n
  4. The Se…I distance is 2.75\u00c5, some 1.13\u00c5 shorter than the combined atom ver der Waals radii (1.90 + 1.98 = 3.88)<\/li>\n
  5. The Wiberg bond index is 0.42 for the Se-I bond and 0.63 for the I-I bond (at the crystal geometry). It is tending towards a symmetrical disposition of the central iodine (a feat also achieved<\/a> by the iodine in the NI3<\/sub> complex).<\/li>\n
  6. The NBO E(2) perturbation involving donation from the Se lone pair into the I-I antibond is 77<\/strong> kcal\/mol, almost twice the value of the one involving DABCO…I-I<\/a>\u00a0and way above the values found for the related hydrogen bond.<\/li>\n
  7. The B3LYP+D3\/Def2-TZVPP+PP(I) optimised structure expands the Se-I bond distance to 3.04 and contracts the I-I distance to 2.81\u00c5 indicating (as with DABCO…I-I) that there may be compression of this bond induced by the lattice.<\/li>\n
  8. The NCI surface shows a classical “strong” interaction between Se and I (blue), but significant additional features arising from the axial hydrogens that might account for the axial orientation of the Se…I-I group.
    \n
    \"Click

    Click for 3D<\/p><\/div><\/li>\n

  9. For good measure, here is the complete crystal structure search, defining any non-bonded contact between any element of group six and group seven that is <0.5\u00c5 shorter than the van del Waals contact. Our candidate is on the left hand edge of the plot.
    \n    \"Se-I\"<\/a><\/p>\n<\/li>\n<\/ol>\n

    References<\/h2>\n
    1. H. Maddox, and J.D. McCullough, \"The Crystal and Molecular Structure of the Iodine Complex of 1-Oxa-4-selenacyclohexane, C<sub>4<\/sub>H<sub>8<\/sub>OSe.I<sub>2<\/sub>\", Inorganic Chemistry<\/i>, vol. 5, pp. 522-526, 1966. https:\/\/doi.org\/10.1021\/ic50038a006<\/a>\n\n<\/li>\n<\/ol>\n\n<\/div> ","protected":false},"excerpt":{"rendered":"

      Continuing my hunt, here is a candidate for a strong(est?) halogen bond, this time between Se and I.. The features of interest include: The six-membered ring is in the chair conformation. The (relatively enormous) I…I substituent is axial! It is attached to the Se rather than the O. The Se…I distance is 2.75\u00c5, some 1.13\u00c5 […]<\/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":false,"_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":[1754,6],"tags":[68,1230],"class_list":["post-13158","post","type-post","status-publish","format-standard","hentry","category-crystal_structure_mining","category-interesting-chemistry","tag-chair","tag-crystal-structure-search"],"jetpack_publicize_connections":[],"jetpack_featured_media_url":"","jetpack_sharing_enabled":true,"jetpack_shortlink":"https:\/\/wp.me\/p1gPyz-3qe","jetpack_likes_enabled":true,"_links":{"self":[{"href":"https:\/\/www.rzepa.net\/blog\/index.php?rest_route=\/wp\/v2\/posts\/13158","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=13158"}],"version-history":[{"count":0,"href":"https:\/\/www.rzepa.net\/blog\/index.php?rest_route=\/wp\/v2\/posts\/13158\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.rzepa.net\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=13158"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.rzepa.net\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=13158"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.rzepa.net\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=13158"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}