{"id":1278,"date":"2009-12-06T11:56:14","date_gmt":"2009-12-06T10:56:14","guid":{"rendered":"http:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=1278"},"modified":"2009-12-08T09:31:17","modified_gmt":"2009-12-08T08:31:17","slug":"the-nature-of-the-c%e2%89%a1s-triple-bond-part-3","status":"publish","type":"post","link":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=1278","title":{"rendered":"The nature of the C\u2261S triple bond: part 3."},"content":{"rendered":"
\n

In the previous two posts<\/a>, a strategy for tuning the nature of the CS bond in the molecule HO-S\u2261C-H was developed, based largely on the lone pair of electrons identified on the carbon atom. By replacing the HO group by one with greater \u03c3-electron withdrawing propensity, the stereo-electronic effect between the O-S bond and the carbon lone pair was enhanced, and in the process, the SC bond was strengthened. It is time to do a control experiment<\/span> in the other direction. Now, the HO-S group is replaced by a H2<\/span>B-S group. The B-S bond, boron being very much less electronegative than oxygen, should be a very poor \u03c3-acceptor. In addition, whereas oxygen was a \u03c0-electron donor (acting to strengthen the S=C region), boron is a \u03c0-acceptor, and will also act in the opposite direction. So now, this group should serve to weaken the S-C bond.<\/p>\n<\/p>\n

\n
\n
\"The<\/dt>\n
The H2BSCH molecule. Click for 3D.<\/dd>\n<\/dl>\n<\/div>\n

At the B3LYP\/cc-pVTZ level (DOI: 10042\/to-3189<\/a>), the S-C bond now emerges as 1.834\u00c5 compared to 1.544\u00c5 for the HO-substituted version and the S-C stretch is reduced to 803 cm-1<\/span>. The NBO interaction term between LP(1)C2 and BD*(1) S1-B3 is indeed quite small (6.9 kcal\/mol). The basin integration for point 10<\/span> increases to 2.22e, whilst point 9<\/span> decreases to 1.90e, and 8<\/span> is again up at 2.11. The SC bond is now merely a single bond!<\/p>\n<\/p>\n

So what have we proved? Well, we find that our hypothesis works in both directions, to either strengthen or weaken the CS region. Indeed, variation of the S-substituent (HO, OTf, BH2) has quite a dramatic effect on the nature of the CS bond, evolving it all the way from a single bond at one extreme to one with significantly triple character at the other.<\/p>\n\n<\/div> ","protected":false},"excerpt":{"rendered":"

In the previous two posts, a strategy for tuning the nature of the CS bond in the molecule HO-S\u2261C-H was developed, based largely on the lone pair of electrons identified on the carbon atom. By replacing the HO group by one with greater \u03c3-electron withdrawing propensity, the stereo-electronic effect between the O-S bond and the […]<\/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":false,"jetpack_social_options":{"image_generator_settings":{"template":"highway","default_image_id":0,"font":"","enabled":false},"version":2}},"categories":[7,4],"tags":[2649,2648],"ppma_author":[2661],"class_list":["post-1278","post","type-post","status-publish","format-standard","hentry","category-hypervalency","category-interesting-chemistry","tag-hypervalency","tag-interesting-chemistry"],"yoast_head":"\nThe nature of the C\u2261S triple bond: part 3. - 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=1278\" \/>\n<meta property=\"og:locale\" content=\"en_GB\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"The nature of the C\u2261S triple bond: part 3. - Henry Rzepa's Blog\" \/>\n<meta property=\"og:description\" content=\"In the previous two posts, a strategy for tuning the nature of the CS bond in the molecule HO-S\u2261C-H was developed, based largely on the lone pair of electrons identified on the carbon atom. By replacing the HO group by one with greater \u03c3-electron withdrawing propensity, the stereo-electronic effect between the O-S bond and the […]\" \/>\n<meta property=\"og:url\" content=\"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=1278\" \/>\n<meta property=\"og:site_name\" content=\"Henry Rzepa's Blog\" \/>\n<meta property=\"article:published_time\" content=\"2009-12-06T10:56:14+00:00\" \/>\n<meta property=\"article:modified_time\" content=\"2009-12-08T08:31:17+00:00\" \/>\n<meta property=\"og:image\" content=\"http:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2009\/12\/CSBH2.jpg\" \/>\n<meta name=\"author\" content=\"Henry Rzepa\" \/>\n<meta name=\"twitter:card\" content=\"summary_large_image\" \/>\n<meta name=\"twitter:label1\" content=\"Written by\" \/>\n\t<meta name=\"twitter:data1\" content=\"Henry Rzepa\" \/>\n\t<meta name=\"twitter:label2\" content=\"Estimated reading time\" \/>\n\t<meta name=\"twitter:data2\" content=\"1 minute\" \/>\n<!-- \/ Yoast SEO plugin. -->","yoast_head_json":{"title":"The nature of the C\u2261S triple bond: part 3. - Henry Rzepa's Blog","robots":{"index":"index","follow":"follow","max-snippet":"max-snippet:-1","max-image-preview":"max-image-preview:large","max-video-preview":"max-video-preview:-1"},"canonical":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=1278","og_locale":"en_GB","og_type":"article","og_title":"The nature of the C\u2261S triple bond: part 3. - Henry Rzepa's Blog","og_description":"In the previous two posts, a strategy for tuning the nature of the CS bond in the molecule HO-S\u2261C-H was developed, based largely on the lone pair of electrons identified on the carbon atom. 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This analysis identified a lone pair of electrons localized on the carbon (integrating in fact to almost exactly 2.0) in addition to electrons in the CC\u2026","rel":"","context":"In "Hypervalency"","block_context":{"text":"Hypervalency","link":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?cat=7"},"img":{"alt_text":"ELF analysis for H-C\u2261S-OTf","src":"https:\/\/i0.wp.com\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2009\/12\/CSOTf.jpg?resize=350%2C200","width":350,"height":200},"classes":[]},{"id":1210,"url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=1210","url_meta":{"origin":1278,"position":1},"title":"The nature of the C\u2261S triple bond","author":"Henry Rzepa","date":"December 1, 2009","format":false,"excerpt":"Steve Bachrach has just blogged on a recent article (DOI: 10.1002\/anie.200903969) claiming the isolation of a compound with a C\u2261S triple bond; Steve notes that Schreiner and co claim a \u201cstructure with a rather strong CS double bond or a weak triple bond\u201d. With this size of molecule, the proverbial\u2026","rel":"","context":"In "Hypervalency"","block_context":{"text":"Hypervalency","link":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?cat=7"},"img":{"alt_text":"A compound with a CS triple bond","src":"https:\/\/i0.wp.com\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2009\/12\/CSCC.jpg?resize=350%2C200","width":350,"height":200},"classes":[]},{"id":19251,"url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=19251","url_meta":{"origin":1278,"position":2},"title":"Are diazomethanes hypervalent molecules? Probably, but in an unexpected way!","author":"Henry Rzepa","date":"December 23, 2017","format":false,"excerpt":"A recently published review on hypervalency introduced a very simple way of quantifying the effect. One of the molecules which was suggested to be hypervalent using this method was diazomethane. Here I take a closer look. The new method is called the valence electron equivalent \u03b3. It is defined as\u00a0\"the\u2026","rel":"","context":"In "Hypervalency"","block_context":{"text":"Hypervalency","link":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?cat=7"},"img":{"alt_text":"","src":"","width":0,"height":0},"classes":[]},{"id":19279,"url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=19279","url_meta":{"origin":1278,"position":3},"title":"Can any hypervalence in diazomethanes be amplified?","author":"Henry Rzepa","date":"December 23, 2017","format":false,"excerpt":"In the previous post, I referred to a recently published review on hypervalency which introduced a very simple way (the\u00a0valence electron equivalent \u03b3)\u00a0of quantifying the effect.\u00a0Diazomethane was cited as one example of a small molecule exhibiting hypervalency (on nitrogen) by this measure. Here I explore the effect of substituting diazomethane\u2026","rel":"","context":"In "Hypervalency"","block_context":{"text":"Hypervalency","link":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?cat=7"},"img":{"alt_text":"","src":"","width":0,"height":0},"classes":[]},{"id":23588,"url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=23588","url_meta":{"origin":1278,"position":4},"title":"Two new reality-based suggestions for molecules with a metal M\u2a78C quadruple bond.","author":"Henry Rzepa","date":"May 8, 2021","format":false,"excerpt":"Following from much discussion over the last decade about the nature of C2, a diatomic molecule which some have suggested sustains a quadruple bond between the two carbon atoms, new ideas are now appearing for molecules in which such a bond may also exist between carbon and a transition metal\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":"https:\/\/i0.wp.com\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2021\/05\/Screenshot-702-300x63.jpg?resize=350%2C200&ssl=1","width":350,"height":200},"classes":[]},{"id":18993,"url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=18993","url_meta":{"origin":1278,"position":5},"title":"VSEPR Theory: Octet-busting or not with trimethyl chlorine, ClMe3.","author":"Henry Rzepa","date":"November 12, 2017","format":false,"excerpt":"A few years back, I took a look at the valence-shell electron pair repulsion approach to the geometry of chlorine trifluoride, ClF3 using so-called ELF basins to locate centroids for both the covalent F-Cl bond electrons and the chlorine lone-pair electrons. Whereas the original VSEPR theory talks about five \"electron\u2026","rel":"","context":"In "Chemical IT"","block_context":{"text":"Chemical IT","link":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?cat=2"},"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\/1278","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=1278"}],"version-history":[{"count":0,"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=\/wp\/v2\/posts\/1278\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=1278"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=1278"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=1278"},{"taxonomy":"author","embeddable":true,"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fppma_author&post=1278"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}