{"id":21009,"date":"2019-06-02T13:52:10","date_gmt":"2019-06-02T12:52:10","guid":{"rendered":"https:\/\/www.ch.imperial.ac.uk\/rzepa\/blog\/?p=21009"},"modified":"2020-04-08T16:52:02","modified_gmt":"2020-04-08T15:52:02","slug":"diatomics-with-eight-valence-electrons-formation-by-radioactive-decay","status":"publish","type":"post","link":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=21009","title":{"rendered":"Diatomics with eight valence-electrons: formation by radioactive decay."},"content":{"rendered":"
\n

This is a follow up to my earlier post<\/a> about C\u2a78N+<\/sup>, itself inspired by this ChemRxiv pre-print[1]<\/a><\/span> which describes a chemical synthesis of singlet biradicaloid C2<\/sub> and its proposed\u00a0identification as such by chemical trapping.<\/p>\n

\"\"<\/a><\/p>\n

First row diatomics based on the iso-electronic principle of eight valence electrons include both C\u2a78N+<\/sup> and C\u2a78C, as well as species such as B\u2a78N, C\u2a78O2+<\/sup>\u00a0and even the unlikely N\u2a78O3+<\/sup>. The diatomic bond is represented here by \u2a78<\/span> which carries the message of six electrons pairing to form a conventional triple bond and the remaining two valence electrons more weakly spin-pairing to form overall a singlet biradicaloid species with a quadruple bond. The “BDE” (bond dissociation energy) of the 4th pair is around 20 kcal\/mol for C\u2a78C,[2]<\/a><\/span> \u00a0which arguably entitles it to be called a weak bond.[3]<\/a><\/span><\/p>\n

Here I am going to explore –<\/sup>B\u2a78N+<\/sup>\u00a0and isoelectronic C\u2a78C via<\/em>\u00a0formation by radioactive decay of tritium into helium (Table, FAIR data DOI: 10.14469\/hpc\/5691<\/a>).<\/p>\n\n\n\n\n\n\n
Entry<\/th>\nsystem<\/th>\n\u0394\u0394G<\/th>\n\u0394\u0394H<\/th>\n<\/tr>\n
1<\/td>\n[Li-C\u2261C-T]\u00a0<\/sup>\u2192 Li-C\u2261C-He+<\/sup>\u00a0+ e \u2192 Li+<\/sup>\u00a0+ C\u2a78C + He\u00a0<\/strong><\/td>\n-44.9<\/td>\n-27.6<\/td>\n<\/tr>\n
2<\/td>\n[(-)C\u2261C-T]\u00a0<\/sup>\u2192 (-)C\u2261C-He+<\/sup>\u00a0+ e \u2192 C\u2a78C + He\u00a0<\/strong><\/td>\n-42.2<\/td>\n-31.9<\/td>\n<\/tr>\n
3<\/td>\n[Li-N\u2261B-T]\u00a0<\/sup>\u2192 Li-N\u2261B-He+<\/sup>\u00a0+ e \u2192 Li+<\/sup>\u00a0+ –<\/sup>B\u2a78N+<\/sup> + He\u00a0<\/strong><\/td>\n-9.0<\/td>\n+2.9<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

The thermochemistry includes a significant contribution from entropy, which favours the reaction. At its simplest, this involves the replacement of a X-He (X=C,B) bond by the 4th C\u2a78X bond. The BDEs (bond dissociation energies) of the X-He bond are very small (< 1 kcal\/mol) and hence the reaction is driven largely by the enthalpy of forming the final C\u2a78X bond, together with entropy increase. Contrast this with the reaction reported above involving cleavage of a C–<\/span>IPh bond,[1]<\/a><\/span> where the C–<\/span>I BDE is\u00a0larger<\/a> (~70-80 kcal\/mol; > 20 kcal\/mol). This makes the reported trapping of C2<\/sub> from this reaction all the more intriguing.<\/p>\n

References<\/h2>\n
  1. K. Miyamoto, S. Narita, Y. Masumoto, T. Hashishin, M. Kimura, M. Ochiai, and M. Uchiyama, \"Room-Temperature Chemical Synthesis of C2\", 2019. https:\/\/doi.org\/10.26434\/chemrxiv.8009633.v1<\/a>\n\n<\/li>\n
  2. D. Danovich, P.C. Hiberty, W. Wu, H.S. Rzepa, and S. Shaik, \"The Nature of the Fourth Bond in the Ground State of C<sub>2<\/sub>: The Quadruple Bond Conundrum\", Chemistry \u2013 A European Journal<\/i>, vol. 20, pp. 6220-6232, 2014. https:\/\/doi.org\/10.1002\/chem.201400356<\/a>\n\n<\/li>\n
  3. S. Shaik, D. Danovich, B. Braida, and P.C. Hiberty, \"The Quadruple Bonding in C<sub>2<\/sub> Reproduces the Properties of the Molecule\", Chemistry \u2013 A European Journal<\/i>, vol. 22, pp. 4116-4128, 2016. https:\/\/doi.org\/10.1002\/chem.201600011<\/a>\n\n<\/li>\n<\/ol>\n\n<\/div> ","protected":false},"excerpt":{"rendered":"

    This is a follow up to my earlier post about C\u2a78N+, itself inspired by this ChemRxiv pre-print which describes a chemical synthesis of singlet biradicaloid C2 and its proposed\u00a0identification as such by chemical trapping. First row diatomics based on the iso-electronic principle of eight valence electrons include both C\u2a78N+ and C\u2a78C, as well as species […]<\/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_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},"categories":[4],"tags":[],"ppma_author":[2661],"class_list":["post-21009","post","type-post","status-publish","format-standard","hentry","category-interesting-chemistry"],"yoast_head":"\nDiatomics with eight valence-electrons: formation by radioactive decay. - 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=21009\" \/>\n<meta property=\"og:locale\" content=\"en_GB\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"Diatomics with eight valence-electrons: formation by radioactive decay. - Henry Rzepa's Blog\" \/>\n<meta property=\"og:description\" content=\"This is a follow up to my earlier post about C\u2a78N+, itself inspired by this ChemRxiv pre-print which describes a chemical synthesis of singlet biradicaloid C2 and its proposed\u00a0identification as such by chemical trapping. First row diatomics based on the iso-electronic principle of eight valence electrons include both C\u2a78N+ and C\u2a78C, as well as species […]\" \/>\n<meta property=\"og:url\" content=\"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=21009\" \/>\n<meta property=\"og:site_name\" content=\"Henry Rzepa's Blog\" \/>\n<meta property=\"article:published_time\" content=\"2019-06-02T12:52:10+00:00\" \/>\n<meta property=\"article:modified_time\" content=\"2020-04-08T15:52:02+00:00\" \/>\n<meta property=\"og:image\" content=\"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2019\/05\/C2.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=\"2 minutes\" \/>\n<!-- \/ Yoast SEO plugin. -->","yoast_head_json":{"title":"Diatomics with eight valence-electrons: formation by radioactive decay. - 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=21009","og_locale":"en_GB","og_type":"article","og_title":"Diatomics with eight valence-electrons: formation by radioactive decay. - Henry Rzepa's Blog","og_description":"This is a follow up to my earlier post about C\u2a78N+, itself inspired by this ChemRxiv pre-print which describes a chemical synthesis of singlet biradicaloid C2 and its proposed\u00a0identification as such by chemical trapping. First row diatomics based on the iso-electronic principle of eight valence electrons include both C\u2a78N+ and C\u2a78C, as well as species […]","og_url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=21009","og_site_name":"Henry Rzepa's Blog","article_published_time":"2019-06-02T12:52:10+00:00","article_modified_time":"2020-04-08T15:52:02+00:00","og_image":[{"url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2019\/05\/C2.svg","type":"","width":"","height":""}],"author":"Henry Rzepa","twitter_card":"summary_large_image","twitter_misc":{"Written by":"Henry Rzepa","Estimated reading time":"2 minutes"},"schema":{"@context":"https:\/\/schema.org","@graph":[{"@type":"Article","@id":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=21009#article","isPartOf":{"@id":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=21009"},"author":{"name":"Henry Rzepa","@id":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/#\/schema\/person\/2b40f7b9c872a4dc1547e040a11b6281"},"headline":"Diatomics with eight valence-electrons: formation by radioactive decay.","datePublished":"2019-06-02T12:52:10+00:00","dateModified":"2020-04-08T15:52:02+00:00","mainEntityOfPage":{"@id":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=21009"},"wordCount":330,"commentCount":0,"image":{"@id":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=21009#primaryimage"},"thumbnailUrl":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2019\/05\/C2.svg","articleSection":["Interesting chemistry"],"inLanguage":"en-GB","potentialAction":[{"@type":"CommentAction","name":"Comment","target":["https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=21009#respond"]}]},{"@type":"WebPage","@id":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=21009","url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=21009","name":"Diatomics with eight valence-electrons: formation by radioactive decay. - 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=21009#primaryimage"},"image":{"@id":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=21009#primaryimage"},"thumbnailUrl":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2019\/05\/C2.svg","datePublished":"2019-06-02T12:52:10+00:00","dateModified":"2020-04-08T15:52:02+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=21009#breadcrumb"},"inLanguage":"en-GB","potentialAction":[{"@type":"ReadAction","target":["https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=21009"]}]},{"@type":"ImageObject","inLanguage":"en-GB","@id":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=21009#primaryimage","url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2019\/05\/C2.svg","contentUrl":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2019\/05\/C2.svg"},{"@type":"BreadcrumbList","@id":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=21009#breadcrumb","itemListElement":[{"@type":"ListItem","position":1,"name":"Home","item":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog"},{"@type":"ListItem","position":2,"name":"Diatomics with eight valence-electrons: formation by radioactive decay."}]},{"@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\/pDef7-5sR","jetpack-related-posts":[{"id":16758,"url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=16758","url_meta":{"origin":21009,"position":0},"title":"What’s in a name? Carbenes: a reality check.","author":"Henry Rzepa","date":"September 11, 2016","format":false,"excerpt":"To quote from Wikipedia: in chemistry, a carbene is a molecule containing a neutral carbon atom with a valence of two and two unshared valence electrons. The most ubiquitous type of carbene of recent times is the one shown below as 1, often referred to as a resonance stabilised or\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":19307,"url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=19307","url_meta":{"origin":21009,"position":1},"title":"Are diazomethanes hypervalent molecules? An attempt into more insight by more “tuning” with substituents.","author":"Henry Rzepa","date":"December 26, 2017","format":false,"excerpt":"Recollect the suggestion\u00a0that diazomethane has hypervalent character. When I looked into this, I came to the conclusion that it probably was mildly hypervalent, but on carbon and not nitrogen. Here I try some variations with substituents to see what light if any this casts. I have expanded the resonance forms\u2026","rel":"","context":"In "Hypervalency"","block_context":{"text":"Hypervalency","link":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?cat=7"},"img":{"alt_text":"","src":"https:\/\/i0.wp.com\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2017\/12\/H2CNCCN_ELF-1024x258.jpg?resize=350%2C200","width":350,"height":200},"classes":[]},{"id":15552,"url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=15552","url_meta":{"origin":21009,"position":2},"title":"VSEPR Theory: A closer look at trifluorothionitrile, NSF3.","author":"Henry Rzepa","date":"January 16, 2016","format":false,"excerpt":"The post on applying VSEPR (\"valence shell electron pair repulsion\") theory to the geometry of ClF3\u00a0has proved perennially popular. So here is a follow-up on another little molecue,\u00a0F3SN. As the name implies, it is often represented with an\u00a0S\u2261N bond. Here I take a look at the conventional analysis. This is\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":2619,"url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=2619","url_meta":{"origin":21009,"position":3},"title":"Hypervalency: I(CN)7 is not hypervalent!","author":"Henry Rzepa","date":"October 17, 2010","format":false,"excerpt":"In the last post, IH7 was examined to see if it might exhibit true hypervalency. The iodine, despite its high coordination, turned out not to be hypervalent, with its (s\/p) valence shell not exceeding eight electrons (and its d-shell still with 10, and the 6s\/6p shells largely unoccupied). Instead, 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":"https:\/\/i0.wp.com\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2010\/10\/ICN7.jpg?resize=350%2C200","width":350,"height":200},"classes":[]},{"id":1691,"url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=1691","url_meta":{"origin":21009,"position":4},"title":"Quintuple bonds","author":"Henry Rzepa","date":"February 16, 2010","format":false,"excerpt":"Climbers scale Mt. Everest, because its there, and chemists have their own version of this. Ever since G. N. Lewis introduced the concept of the electron-pair bond in 1916, the idea of a bond as having a formal bond-order has been seen as a useful way of thinking about molecules.\u2026","rel":"","context":"In "Hypervalency"","block_context":{"text":"Hypervalency","link":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?cat=7"},"img":{"alt_text":"","src":"https:\/\/i0.wp.com\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2010\/02\/Cr.jpg?resize=350%2C200","width":350,"height":200},"classes":[]},{"id":15823,"url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=15823","url_meta":{"origin":21009,"position":5},"title":"Real hypervalency in a small molecule.","author":"Henry Rzepa","date":"February 21, 2016","format":false,"excerpt":"Hypervalency is defined as a molecule\u00a0that contains one or more main group elements formally bearing more than eight\u00a0 electrons in their\u00a0 valence shell. One example of a molecule so characterised was CLi6 where the description \"\u201ccarbon can expand its octet of electrons to form this relatively stable molecule\u201c was used.\u2026","rel":"","context":"In "Bond slam"","block_context":{"text":"Bond slam","link":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?cat=2237"},"img":{"alt_text":"CH4","src":"https:\/\/i0.wp.com\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2016\/02\/CH4.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\/21009","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=21009"}],"version-history":[{"count":29,"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=\/wp\/v2\/posts\/21009\/revisions"}],"predecessor-version":[{"id":22058,"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=\/wp\/v2\/posts\/21009\/revisions\/22058"}],"wp:attachment":[{"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=21009"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=21009"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=21009"},{"taxonomy":"author","embeddable":true,"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fppma_author&post=21009"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}