{"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_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,"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}},"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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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. 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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":28773,"url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=28773","url_meta":{"origin":28639,"position":2},"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":28407,"url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=28407","url_meta":{"origin":28639,"position":3},"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":[]},{"id":11279,"url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=11279","url_meta":{"origin":28639,"position":4},"title":"An example of an extreme gauche effect: FSSF.","author":"Henry Rzepa","date":"September 21, 2013","format":false,"excerpt":"The best known example of the gauche effect is 1,2-difluoroethane, which exhibits a relatively small preference of ~0.5 kcal\/mol for this conformer over the anti orientation, which is also a minimum. But FSSF, which I discussed in the previous post, beats this hands down! It also, by the way, must\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":"FSSF-ELF","src":"https:\/\/i0.wp.com\/www.ch.imperial.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2013\/09\/FSSF-ELF.jpg?resize=350%2C200","width":350,"height":200},"classes":[]},{"id":16987,"url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=16987","url_meta":{"origin":28639,"position":5},"title":"Catenated atoms and groups.","author":"Henry Rzepa","date":"October 13, 2016","format":false,"excerpt":"Chemists are as fond of records as any, although I doubt you will find many\u00a0chemical ones\u00a0in 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 and the record\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","0":null,"1":"","2":"","3":"","4":"","5":"","6":"","7":"","8":""}],"_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}]}}