{"id":17115,"date":"2016-11-30T11:32:48","date_gmt":"2016-11-30T11:32:48","guid":{"rendered":"http:\/\/www.ch.imperial.ac.uk\/rzepa\/blog\/?p=17115"},"modified":"2016-12-03T10:17:02","modified_gmt":"2016-12-03T10:17:02","slug":"long-c-c-bonds","status":"publish","type":"post","link":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=17115","title":{"rendered":"Long C-C bonds."},"content":{"rendered":"
\n

In an earlier post, I searched<\/a> for small C-C-C angles, finding one example that was also accompanied by an apparently exceptionally long C-C bond (2.18\u00c5). But this arose from highly unusual bonding giving rise not to a single bond order but one closer to one half! How long can a “normal” (i.e<\/em> single) C-C bond get, a question which has long fascinated chemists.<\/p>\n

A naive search of the CSD is not as straightforward as it seems. Using the simple sub-structure R3<\/sub>C-CR3<\/sub>\u00a0as the search query gives LIRPEI, DOI:\u00a010.5517\/CCQ043Y<\/a>[1]<\/a><\/span> an apparently unexceptional molecule with a very exceptional C-C distance of 1.87\u00c5. With long bonds one has to be ultra-careful to look at the crystallographic analysis before drawing any conclusions. One class of molecule where this has been done by many groups is the system shown below (red = long bond), with 47 entries and for which\u00a0the longest C-C bond emerges with the value of 1.79\u00c5[2]<\/a><\/span><\/p>\n

 <\/p>\n

\"long-bonds\"<\/a><\/p>\n

\"long-cc\"<\/p>\n

You can view this structure at DOI:\u00a010.5517\/CCS0R6Q<\/a>[3]<\/a><\/span> and the authors go to some pains to assure us that it is still a closed shell single bond, and not a biradical. That does seem to be the current record holder, but of course we are only talking here about molecules whose crystal structure has been determined.<\/p>\n

I will end with an open question; how SHORT could a “single” C-C bond get? Here, a search of the CSD is entirely dominated by crystallographic artefacts, and I am not sure what the value might be.\u00a0<\/p>\n

References<\/h2>\n
  1. Zhang, Jian., Chen, Shumei., Valle, H.., Wong, M.., Austria, C.., Cruz, M.., and Bu, Xianhui., \"CCDC 655529: Experimental Crystal Structure Determination\", 2008. https:\/\/doi.org\/10.5517\/ccq043y<\/a>\n\n<\/li>\n
  2. T. Takeda, H. Kawai, R. Herges, E. Mucke, Y. Sawai, K. Murakoshi, K. Fujiwara, and T. Suzuki, \"Negligible diradical character for the ultralong C\u2013C bond in 1,1,2,2-tetraarylpyracene derivatives at room temperature\", Tetrahedron Letters<\/i>, vol. 50, pp. 3693-3697, 2009. https:\/\/doi.org\/10.1016\/j.tetlet.2009.03.202<\/a>\n\n<\/li>\n
  3. Takeda, T.., Kawai, H.., Herges, R.., Mucke, E.., Sawai, Y.., Murakoshi, K.., Fujiwara, K.., and Suzuki, T.., \"CCDC 715703: Experimental Crystal Structure Determination\", 2010. https:\/\/doi.org\/10.5517\/ccs0r6q<\/a>\n\n<\/li>\n<\/ol>\n\n<\/div> ","protected":false},"excerpt":{"rendered":"

    In an earlier post, I searched for small C-C-C angles, finding one example that was also accompanied by an apparently exceptionally long C-C bond (2.18\u00c5). But this arose from highly unusual bonding giving rise not to a single bond order but one closer to one half! How long can a “normal” (i.e single) C-C bond […]<\/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,"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":[1745,4],"tags":[1901,1900,1759,1402,557,1902,734,1015],"ppma_author":[2661],"class_list":["post-17115","post","type-post","status-publish","format-standard","hentry","category-crystal_structure_mining","category-interesting-chemistry","tag-aviation","tag-bond-order","tag-carbon-carbon-bond","tag-chemical-bond","tag-chemical-bonding","tag-naive-search","tag-search-query","tag-single-bond"],"yoast_head":"\nLong C-C bonds. - 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=17115\" \/>\n<meta property=\"og:locale\" content=\"en_GB\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"Long C-C bonds. - Henry Rzepa's Blog\" \/>\n<meta property=\"og:description\" content=\"In an earlier post, I searched for small C-C-C angles, finding one example that was also accompanied by an apparently exceptionally long C-C bond (2.18\u00c5). But this arose from highly unusual bonding giving rise not to a single bond order but one closer to one half! How long can a “normal” (i.e single) C-C bond […]\" \/>\n<meta property=\"og:url\" content=\"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=17115\" \/>\n<meta property=\"og:site_name\" content=\"Henry Rzepa's Blog\" \/>\n<meta property=\"article:published_time\" content=\"2016-11-30T11:32:48+00:00\" \/>\n<meta property=\"article:modified_time\" content=\"2016-12-03T10:17:02+00:00\" \/>\n<meta property=\"og:image\" content=\"http:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2016\/11\/long-bonds.svg\" \/>\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":"Long C-C bonds. - 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=17115","og_locale":"en_GB","og_type":"article","og_title":"Long C-C bonds. - Henry Rzepa's Blog","og_description":"In an earlier post, I searched for small C-C-C angles, finding one example that was also accompanied by an apparently exceptionally long C-C bond (2.18\u00c5). But this arose from highly unusual bonding giving rise not to a single bond order but one closer to one half! How long can a “normal” (i.e single) C-C bond […]","og_url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=17115","og_site_name":"Henry Rzepa's Blog","article_published_time":"2016-11-30T11:32:48+00:00","article_modified_time":"2016-12-03T10:17:02+00:00","og_image":[{"url":"http:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2016\/11\/long-bonds.svg","type":"","width":"","height":""}],"author":"Henry Rzepa","twitter_card":"summary_large_image","twitter_misc":{"Written by":"Henry Rzepa","Estimated reading time":"1 minute"},"schema":{"@context":"https:\/\/schema.org","@graph":[{"@type":"Article","@id":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=17115#article","isPartOf":{"@id":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=17115"},"author":{"name":"Henry Rzepa","@id":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/#\/schema\/person\/2b40f7b9c872a4dc1547e040a11b6281"},"headline":"Long C-C bonds.","datePublished":"2016-11-30T11:32:48+00:00","dateModified":"2016-12-03T10:17:02+00:00","mainEntityOfPage":{"@id":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=17115"},"wordCount":266,"commentCount":0,"image":{"@id":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=17115#primaryimage"},"thumbnailUrl":"http:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2016\/11\/long-bonds.svg","keywords":["Aviation","Bond order","Carbon\u2013carbon bond","Chemical bond","chemical bonding","naive search","search query","single bond"],"articleSection":["crystal_structure_mining","Interesting chemistry"],"inLanguage":"en-GB","potentialAction":[{"@type":"CommentAction","name":"Comment","target":["https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=17115#respond"]}]},{"@type":"WebPage","@id":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=17115","url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=17115","name":"Long C-C bonds. - Henry Rzepa's Blog","isPartOf":{"@id":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/#website"},"primaryImageOfPage":{"@id":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=17115#primaryimage"},"image":{"@id":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=17115#primaryimage"},"thumbnailUrl":"http:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2016\/11\/long-bonds.svg","datePublished":"2016-11-30T11:32:48+00:00","dateModified":"2016-12-03T10:17:02+00:00","author":{"@id":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/#\/schema\/person\/2b40f7b9c872a4dc1547e040a11b6281"},"breadcrumb":{"@id":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=17115#breadcrumb"},"inLanguage":"en-GB","potentialAction":[{"@type":"ReadAction","target":["https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=17115"]}]},{"@type":"ImageObject","inLanguage":"en-GB","@id":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=17115#primaryimage","url":"http:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2016\/11\/long-bonds.svg","contentUrl":"http:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2016\/11\/long-bonds.svg"},{"@type":"BreadcrumbList","@id":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=17115#breadcrumb","itemListElement":[{"@type":"ListItem","position":1,"name":"Home","item":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog"},{"@type":"ListItem","position":2,"name":"Long C-C bonds."}]},{"@type":"WebSite","@id":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/#website","url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/","name":"Henry Rzepa's Blog","description":"Chemistry with a twist","potentialAction":[{"@type":"SearchAction","target":{"@type":"EntryPoint","urlTemplate":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?s={search_term_string}"},"query-input":{"@type":"PropertyValueSpecification","valueRequired":true,"valueName":"search_term_string"}}],"inLanguage":"en-GB"},{"@type":"Person","@id":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/#\/schema\/person\/2b40f7b9c872a4dc1547e040a11b6281","name":"Henry Rzepa","image":{"@type":"ImageObject","inLanguage":"en-GB","@id":"https:\/\/secure.gravatar.com\/avatar\/897b6740f7f599bca7942cdf7d7914af5988937ae0e3869ab09aebb87f26a731?s=96&d=blank&r=g370be3a7397865e4fd161aefeb0a5a85","url":"https:\/\/secure.gravatar.com\/avatar\/897b6740f7f599bca7942cdf7d7914af5988937ae0e3869ab09aebb87f26a731?s=96&d=blank&r=g","contentUrl":"https:\/\/secure.gravatar.com\/avatar\/897b6740f7f599bca7942cdf7d7914af5988937ae0e3869ab09aebb87f26a731?s=96&d=blank&r=g","caption":"Henry Rzepa"},"description":"Henry Rzepa is Emeritus Professor of Computational Chemistry at Imperial College London.","sameAs":["https:\/\/orcid.org\/0000-0002-8635-8390"],"url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?author=1"}]}},"jetpack_publicize_connections":[],"jetpack_featured_media_url":"","jetpack_sharing_enabled":true,"jetpack_shortlink":"https:\/\/wp.me\/pDef7-4s3","jetpack-related-posts":[{"id":17122,"url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=17122","url_meta":{"origin":17115,"position":0},"title":"Long C=C bonds.","author":"Henry Rzepa","date":"December 1, 2016","format":false,"excerpt":"Following on from a search for long C-C bonds, here is the same repeated for C=C double bonds. The query restricts the search to each carbon having just two non-metallic substituents. To avoid conjugation with these, they each are 4-coordinated; the carbons themselves are three-coordinated. Further constraints are the usual\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":"sq","src":"https:\/\/i0.wp.com\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2016\/12\/sq-1024x415.jpg?resize=350%2C200","width":350,"height":200},"classes":[]},{"id":27788,"url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=27788","url_meta":{"origin":17115,"position":1},"title":"A carbon-carbon one-electron bond! Or a weak carbon-carbon interaction?","author":"Henry Rzepa","date":"October 1, 2024","format":false,"excerpt":"More than 100 years ago, before the quantum mechanical treatment of molecules had been formulated, G. N. Lewis proposed a simple model for chemical bonding that is still taught today. This is the idea of the three categories of bond we know as single, double and triple, comprising respectively two,\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":18950,"url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=18950","url_meta":{"origin":17115,"position":2},"title":"Elongating an N-B single bond is much easier than stretching a C-C single bond.","author":"Henry Rzepa","date":"October 24, 2017","format":false,"excerpt":"An N-B single bond is iso-electronic to a C-C single bond, as per below. So here is a simple question: what form does the distribution of the lengths of these two bonds take, as obtained from crystal structures?\u00a0 The Conquest search query is very simple (no disorder, no errors). When\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\/2017\/10\/C-C-1024x804.jpg?resize=350%2C200","width":350,"height":200},"classes":[]},{"id":16819,"url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=16819","url_meta":{"origin":17115,"position":3},"title":"What\u2019s in a name? Stabilised “nitrenes”.","author":"Henry Rzepa","date":"September 19, 2016","format":false,"excerpt":"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\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":"nitrene1","src":"https:\/\/i0.wp.com\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2016\/09\/nitrene1-1024x655.jpg?resize=350%2C200","width":350,"height":200},"classes":[]},{"id":18277,"url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=18277","url_meta":{"origin":17115,"position":4},"title":"How does carbon dioxide coordinate to a metal?","author":"Henry Rzepa","date":"May 6, 2017","format":false,"excerpt":"Mention carbon dioxide (CO2) to most chemists and its properties as a metal ligand are not the first aspect that springs to mind. Here thought I might take a look at how it might act as such. There are up to\u00a0five binding modes with one metal that one might envisage:\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\/2017\/05\/078.jpg?resize=350%2C200","width":350,"height":200},"classes":[]},{"id":18165,"url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=18165","url_meta":{"origin":17115,"position":5},"title":"\u03c0-Facial hydrogen bonds to alkenes (revisited): how close can an acidic hydrogen approach?","author":"Henry Rzepa","date":"April 15, 2017","format":false,"excerpt":"Back in the early 1990s, we first discovered the delights of searching crystal structures\u00a0for unusual\u00a0bonding features. One of the first cases was a search for hydrogen bonds formed to the\u00a0\u03c0-faces of alkenes and alkynes. In those days the CSD database of crystal structures was a lot smaller (<80,000 structures; it's\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\/2017\/04\/SQ-H-pi-1024x783.jpg?resize=350%2C200","width":350,"height":200},"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\/17115","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=17115"}],"version-history":[{"count":4,"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=\/wp\/v2\/posts\/17115\/revisions"}],"predecessor-version":[{"id":17121,"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=\/wp\/v2\/posts\/17115\/revisions\/17121"}],"wp:attachment":[{"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=17115"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=17115"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=17115"},{"taxonomy":"author","embeddable":true,"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fppma_author&post=17115"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}