{"id":28639,"date":"2025-05-21T09:48:21","date_gmt":"2025-05-21T08:48:21","guid":{"rendered":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=28639"},"modified":"2025-05-29T12:09:57","modified_gmt":"2025-05-29T11:09:57","slug":"s7i1-the-largest-anomeric-effect-exhibited-by-sulfur","status":"publish","type":"post","link":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=28639","title":{"rendered":"S7<\/sub>I1+<\/sup>: The largest anomeric effect exhibited by sulfur."},"content":{"rendered":"
\n

In this series of posts about the electronic effects in small sulfur rings[1]<\/a><\/span> I have explored increasingly large induced geometric effects. Here is the largest so far, for the compound S7<\/sub>I1+<\/sup>[2]<\/a><\/span><\/p>\n

\"\"<\/a>
\nThe calculated geometry[3]<\/a><\/span> is shown below, with the crystallographic values in parentheses – the two matching very well.<\/p>\n

\"\"<\/p>\n

The calculated NBO7 stereoelectronic analysis identifies an especially strong donor (S7) interaction with an acceptor S4-S7, the E(2) energy being 36.9 kcal\/mol. The Wiberg S4-S5 bond index is 0.512 and the S-S stretching wavenumber is ν 131. The Wiberg index for S4-S7 is 1.4618 and the S-S stretch ν 667 cm-1<\/sup>, matching the shortest bond.<\/p>\n

The electronic overlap is shown below (click on image to view as a 3D model). <\/p>\n

\"\" <\/p>\n

So we end with the current record for an SLp<\/sub>\/SSσ*<\/sub> interaction of 36.9 kcal\/mol. Who would have thought that small sulfur rings could be such fun!<\/p>\n

References<\/h2>\n
  1. H. Rzepa, \"5-Imino-5\u03bb<sup>4<\/sup>-heptathiepane 3-oxide. More exuberent anomeric effects.\", 2025. https:\/\/doi.org\/10.59350\/rzepa.28615<\/a>\n\n<\/li>\n
  2. J. Passmore, G. Sutherland, P. Taylor, T.K. Whidden, and P.S. White, \"Preparations and x-ray crystal structures of iodo-cyclo-heptasulfur hexafluoroantimonate(V) and hexafluoroarsenate(V), S7ISbF6 and S7IAsF6\", Inorganic Chemistry<\/i>, vol. 20, pp. 3839-3845, 1981. https:\/\/doi.org\/10.1021\/ic50225a048<\/a>\n\n<\/li>\n
  3. H. Rzepa, \"S7I(+) ax G = -3083.654991\", 2025. https:\/\/doi.org\/10.14469\/hpc\/15236<\/a>\n\n<\/li>\n<\/ol>\n\n<\/div> ","protected":false},"excerpt":{"rendered":"

    In this series of posts about the electronic effects in small sulfur rings I have explored increasingly large induced geometric effects. Here is the largest so far, for the compound S7I1+ The calculated geometry is shown below, with the crystallographic values in parentheses – the two matching very well. The calculated NBO7 stereoelectronic analysis identifies […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_jetpack_newsletter_access":"","_jetpack_dont_email_post_to_subs":false,"_jetpack_newsletter_tier_id":0,"_jetpack_memberships_contains_paywalled_content":false,"_jetpack_feature_clip_id":0,"_jetpack_memberships_contains_paid_content":false,"activitypub_content_warning":"","activitypub_content_visibility":"","activitypub_max_image_attachments":5,"activitypub_interaction_policy_quote":"anyone","activitypub_status":"","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},"jetpack_post_was_ever_published":false,"_ppma_block_editor_authors":""},"categories":[4,1086],"tags":[],"ppma_author":[2661],"class_list":["post-28639","post","type-post","status-publish","format-standard","hentry","category-interesting-chemistry","category-reaction-mechanism-2"],"yoast_head":"\nS7I1+: The largest anomeric effect exhibited by sulfur. - Henry Rzepa's Blog<\/title>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=28639\" \/>\n<meta property=\"og:locale\" content=\"en_GB\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"S7I1+: The largest anomeric effect exhibited by sulfur. - Henry Rzepa's Blog\" \/>\n<meta property=\"og:description\" content=\"In this series of posts about the electronic effects in small sulfur rings I have explored increasingly large induced geometric effects. 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More exuberent anomeric effects.","author":"Henry Rzepa","date":"May 20, 2025","format":false,"excerpt":"The two previous \u00a0posts, on the topic of anomeric effects in 7-membered sulfur rings illustrated how orbital interactions between the lone pairs in the molecules and S-S bonds produced widely varying S-S bond lengths in the molecules, some are shorter than normal (which is ~2.05\u00c5 for e.g. the S8 ring)\u2026","rel":"","context":"In "Interesting chemistry"","block_context":{"text":"Interesting chemistry","link":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?cat=4"},"img":{"alt_text":"","src":"","width":0,"height":0},"classes":[]},{"id":28515,"url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=28515","url_meta":{"origin":28639,"position":1},"title":"Cycloheptasulfur sulfoxide, S7O – Anomeric effects galore!","author":"Henry Rzepa","date":"May 19, 2025","format":false,"excerpt":"The monosulfoxide of cyclo-heptasulfur was reported along with cycloheptasulfur itself in 1977, along with the remarks that \"The \u03b4 modification of S7 contains bonds of widely differing length: this has never been observed before in an unsubstituted molecule. and \"the same effect having also been observed in other sulfur rings\u2026","rel":"","context":"In "Interesting chemistry"","block_context":{"text":"Interesting chemistry","link":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?cat=4"},"img":{"alt_text":"","src":"","width":0,"height":0},"classes":[]},{"id":32008,"url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=32008","url_meta":{"origin":28639,"position":2},"title":"Exploring the effect that causes ring-size specificity of transition metals for polysulfide dianions: Cyclopentadienyl-2,6-di-isopropylphenoxy Titanium pentasulfide.","author":"Henry Rzepa","date":"September 14, 2026","format":false,"excerpt":"In the previous post we described the orbital interactions involved in stabilising the formation of a Cp2TiS5 complex (figure 1 below, X=S) rather than a Cp2TiS4 complex when Cp2TiCl2 is treated with a mixture of polysulfide dianions - and how these interactions can be \"tuned\" by variation in the ring\u2026","rel":"","context":"In "crystal_structure_mining"","block_context":{"text":"crystal_structure_mining","link":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?cat=1745"},"img":{"alt_text":"","src":"","width":0,"height":0},"classes":[]},{"id":28773,"url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=28773","url_meta":{"origin":28639,"position":3},"title":"Cyclo-S6 (Hexathiane) – anomeric effects again!","author":"Henry Rzepa","date":"June 1, 2025","format":false,"excerpt":"I thought I was done with exploring anomeric effects in small sulfur rings. However, I then realised that all the systems\u00a0that I had described had an odd number of atoms and that I had not looked at any even numbered rings. Thus hexasulfur is a smaller (known) ring version of\u2026","rel":"","context":"In "Interesting chemistry"","block_context":{"text":"Interesting chemistry","link":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?cat=4"},"img":{"alt_text":"","src":"","width":0,"height":0},"classes":[]},{"id":31892,"url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=31892","url_meta":{"origin":28639,"position":4},"title":"Identifying the origins of the ring-size specificity of transition metals for polysulfide anions: “tuning” the effect.","author":"Henry Rzepa","date":"September 10, 2026","format":false,"excerpt":"A recently published article addresses the long standing problem of why transition metals complexes such as e.g. Cp2TiCl2 in the presence of solutions of polysulfide dianions containing sulfur chains of various lengths, can react to form sulfur ring complexes of a specific size, depending on the metal. Thus when the\u2026","rel":"","context":"In "Interesting chemistry"","block_context":{"text":"Interesting chemistry","link":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?cat=4"},"img":{"alt_text":"","src":"","width":0,"height":0},"classes":[]},{"id":28407,"url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=28407","url_meta":{"origin":28639,"position":5},"title":"Cyclo-Heptasulfur, S7 – a classic anomeric effect discovered during a pub lunch!","author":"Henry Rzepa","date":"May 16, 2025","format":false,"excerpt":"Way back in 1977, the crystal structure of the sulfur ring S7 was reported. The authors noted that \"The \u03b4 modification of S7 contains bonds of widely differing length: this has never been observed before in an unsubstituted molecule.\" No explanation was offered, although they note that similar effects have\u2026","rel":"","context":"In "crystal_structure_mining"","block_context":{"text":"crystal_structure_mining","link":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?cat=1745"},"img":{"alt_text":"","src":"","width":0,"height":0},"classes":[]}],"jetpack_likes_enabled":false,"authors":[{"term_id":2661,"user_id":1,"is_guest":0,"slug":"admin","display_name":"Henry Rzepa","avatar_url":"https:\/\/secure.gravatar.com\/avatar\/897b6740f7f599bca7942cdf7d7914af5988937ae0e3869ab09aebb87f26a731?s=96&d=blank&r=g","author_category":"1","first_name":"Henry","last_name":"Rzepa","user_url":"https:\/\/orcid.org\/0000-0002-8635-8390","job_title":"","description":"Emeritus Professor of Computational Chemistry at Imperial College London."}],"jetpack_featured_media_url":"","_links":{"self":[{"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=\/wp\/v2\/posts\/28639","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=28639"}],"version-history":[{"count":32,"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=\/wp\/v2\/posts\/28639\/revisions"}],"predecessor-version":[{"id":28757,"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=\/wp\/v2\/posts\/28639\/revisions\/28757"}],"wp:attachment":[{"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=28639"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=28639"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=28639"},{"taxonomy":"author","embeddable":true,"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fppma_author&post=28639"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}