{"id":18993,"date":"2017-11-12T08:47:42","date_gmt":"2017-11-12T08:47:42","guid":{"rendered":"http:\/\/www.ch.imperial.ac.uk\/rzepa\/blog\/?p=18993"},"modified":"2017-11-21T12:59:41","modified_gmt":"2017-11-21T12:59:41","slug":"vsepr-theory-octet-busting-or-not-and-with-trimethyl-chlorine-clme3","status":"publish","type":"post","link":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=18993","title":{"rendered":"VSEPR Theory: Octet-busting or not with trimethyl chlorine, ClMe3."},"content":{"rendered":"
\n

A few years back, I took a look at the valence-shell electron pair repulsion<\/a> approach to the geometry of chlorine trifluoride, ClF3<\/sub> 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 pairs”<\/a> totalling an octet-busting ten electrons surrounding chlorine, the electron density-based ELF approach located only ~6.8e surrounding the central chlorine and no “octet-busting”. The remaining electrons occupied fluorine lone pairs rather than the shared Cl-F regions. Here I take a look at ClMe3<\/sub>, as induced by the analysis of SeMe6<\/sub><\/a>.<\/p>\n

The difference between\u00a0ClF3 <\/sub>and\u00a0ClMe3\u00a0<\/sub>is that octet-excess electrons (two in this case) in the former can relocate into fluorine lone pairs by occupying in effect anti-bonding orbitals and hence end up not contributing to the central atom valence shell.\u2021<\/sup> With\u00a0ClMe3<\/sub> the methyl groups cannot apparently sustain such lone pairs, at least not distinct from the Cl-C bond region. So might we get an octet-busting example with this molecule? A ClMe3<\/sub>\u00a0calculation (\u03c9b97xd\/6-311++g(d,p)) reveals a molecule with all real vibrational modes (i.e.<\/em> a minimum, FAIR data DOI:\u00a010.14469\/hpc\/3241<\/a>) and ELF (FAIR data DOI\u00a010.14469\/hpc\/3242<\/a>)\u2020<\/sup> basins as shown below:<\/p>\n

\"\"<\/p>\n

Density-derived approach:<\/strong> Two of the C-Cl bonds each exhibit two<\/strong> ELF basins; one disynaptic basin (0.94e) and one monosynaptic basin (0.20e) closer to the chlorine. The former pair integrate to 1.88e, density which largely arises from carbon (natural charge -0.84) and which contribute to a total integration for these carbons of 7.17e. The latter pair contributes to a total chlorine integration\u00a0of 7.19e. The angle subtended at chlorine for the two 2.68e “lone pair” basins is 141\u00b0. Thus an inner, octet-compliant, valence-shell for chlorine is revealed, plus an expanded-octet outer one into which the two additional electrons go. The latter contribute to forming an octet-compliant carbon valence shell, but may be considered as not<\/strong> contributing to the valence shell of the other atom of the pair, the chlorine. An endo\u00a0<\/em>lone-pair rather than the more usual exo\u00a0<\/em>lone-pair if you will. These results reveal that the molecular feature we know as a (single) “bond” may in fact have more complex inner structures or zones, something we do not normally consider bonds as having. In this model, these zones are not invariably considered as shared between both the atoms comprising the bond.<\/p>\n

Orbital-derived approach:<\/strong> NBO analysis (FAIR data DOI: 10.14469\/hpc\/3241<\/a>)\u00a0reveals the chlorine electronic configuration as [core]3S(1.83)3p(4.67)4S(0.01)3d(0.03)5p(0.02,) showing very little population of the Rydberg shells (4s, 3d, 5p) occurs (0.13e in total). This method of partitioning the electrons allocates a chlorine Wiberg bond index of 2.00 and the methyl carbon bond index of\u00a0\u00a03.83. If the regular valence of Cl is taken as 1, then the central chlorine can be regarded as non-Rydberg hypervalent<\/strong> (the electrons in the 0.94e basins are taken as contributing to the chlorine bond index).<\/p>\n

The carbon-halogen bond internal structures simplify for Br (DOI: 10.14469\/hpc\/3248<\/a>, 10.14469\/hpc\/3250<\/a>) and I (DOI: 10.14469\/hpc\/3249<\/a>, 10.14469\/hpc\/3247<\/a>); for each only a single ELF basin is located and the NBO Br and I bond indices are respectively 2.10 and 2.1. This is not due to incursion of \u00a0Rydberg hypervalence (Br:\u00a0[core]4S(1.83)4p(4.46)5S(0.02)4d(0.03)6p( 0.01); I:\u00a0[core]5S(1.82)5p(4.29)6S(0.02)5d(0.02)6p(0.01) ) but of a merging of the carbon and halogen valence basin such that the ELF contributions to each cannot be deconvoluted. In each case the NBO bond indices of ~2 suggest hypervalency for the halogen.<\/p>\n

\"\"<\/p>\n

\"\"<\/p>\n

What have we learnt? \u00a0That the shared electron (covalent) bond can have complex internal features, such as two discrete basins for the apparently shared electrons. How one partitions these electrons can influence the value one obtains for the total shared electron count and hence whether the octet is retained or expanded for main group elements such as the halogens. And finally, that hypervalence and hyper-coordination are related in the orbital model at least. Thus along the series Men<\/sub>I (n= coordination number 1,3,5,7), the values of the Wiberg bond index at the halogen progress as 1.0, 2.1, 3.1 (DOI: 10.14469\/hpc\/3236<\/a>) and 4.01 (DOI: 10.14469\/hpc\/3238<\/a>), or one extra atom bond index per electron pair. \u00a0Given this, it seems useful to retain the distinction between the terms hypervalence and hyper-coordination, but also recognize that we still may have much to learn about the former.<\/p>\n

\n

\u2021<\/sup>See the previous post on SeMe6<\/sub><\/a> for a more detailed discussion.<\/p>\n

\u2020\u00a0<\/sup>The FAIR Data<\/a> accompanying this blog post is organised in a new way here. All the calculations are collected together with an over-arching DOI:\u00a010.14469\/hpc\/3252<\/a>\u00a0associated with this post, with individual entries accessible directly using the DOIs given above. The post itself has a \u00a0DOI:\u00a010.14469\/hpc\/3255<\/a>\u00a0and the two identifiers are associated with each-other via<\/em> their respective metadata. \u00a0A set of standards (https:\/\/jats.nlm.nih.gov<\/a>) with implementation guidelines for e.g. repositories<\/a>, authors<\/a> and publishers-editors\u00a0<\/a>\u00a0are expected in the future to establish infra-structures for cross-linking narratives\/stories with the data on which they are based.<\/p>\n\n<\/div> ","protected":false},"excerpt":{"rendered":"

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 pairs” totalling an octet-busting ten […]<\/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":[2,7],"tags":[1402,557,1395,2010,1519,1518,1433,1512,1560,1634,1517],"ppma_author":[2661],"class_list":["post-18993","post","type-post","status-publish","format-standard","hentry","category-chemical-it","category-hypervalency","tag-chemical-bond","tag-chemical-bonding","tag-chemistry","tag-chlorine","tag-covalent-bond","tag-lone-pair","tag-oxidizing-agents","tag-quantum-chemistry","tag-stereochemistry","tag-valence","tag-vsepr-theory"],"yoast_head":"\nVSEPR Theory: Octet-busting or not with trimethyl chlorine, ClMe3. - 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=18993\" \/>\n<meta property=\"og:locale\" content=\"en_GB\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"VSEPR Theory: Octet-busting or not with trimethyl chlorine, ClMe3. - Henry Rzepa's Blog\" \/>\n<meta property=\"og:description\" content=\"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 pairs” totalling an octet-busting ten […]\" \/>\n<meta property=\"og:url\" content=\"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=18993\" \/>\n<meta property=\"og:site_name\" content=\"Henry Rzepa's Blog\" \/>\n<meta property=\"article:published_time\" content=\"2017-11-12T08:47:42+00:00\" \/>\n<meta property=\"article:modified_time\" content=\"2017-11-21T12:59:41+00:00\" \/>\n<meta property=\"og:image\" content=\"http:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2017\/11\/348.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=\"4 minutes\" \/>\n<!-- \/ Yoast SEO plugin. -->","yoast_head_json":{"title":"VSEPR Theory: Octet-busting or not with trimethyl chlorine, ClMe3. - 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=18993","og_locale":"en_GB","og_type":"article","og_title":"VSEPR Theory: Octet-busting or not with trimethyl chlorine, ClMe3. - Henry Rzepa's Blog","og_description":"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 pairs” totalling an octet-busting ten […]","og_url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=18993","og_site_name":"Henry Rzepa's Blog","article_published_time":"2017-11-12T08:47:42+00:00","article_modified_time":"2017-11-21T12:59:41+00:00","og_image":[{"url":"http:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2017\/11\/348.jpg","type":"","width":"","height":""}],"author":"Henry Rzepa","twitter_card":"summary_large_image","twitter_misc":{"Written by":"Henry Rzepa","Estimated reading time":"4 minutes"},"schema":{"@context":"https:\/\/schema.org","@graph":[{"@type":"Article","@id":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=18993#article","isPartOf":{"@id":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=18993"},"author":{"name":"Henry Rzepa","@id":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/#\/schema\/person\/2b40f7b9c872a4dc1547e040a11b6281"},"headline":"VSEPR Theory: Octet-busting or not with trimethyl chlorine, ClMe3.","datePublished":"2017-11-12T08:47:42+00:00","dateModified":"2017-11-21T12:59:41+00:00","mainEntityOfPage":{"@id":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=18993"},"wordCount":831,"commentCount":5,"image":{"@id":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=18993#primaryimage"},"thumbnailUrl":"http:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2017\/11\/348.jpg","keywords":["Chemical bond","chemical bonding","Chemistry","Chlorine","Covalent bond","Lone pair","Oxidizing agents","Quantum chemistry","Stereochemistry","Valence","VSEPR theory"],"articleSection":["Chemical IT","Hypervalency"],"inLanguage":"en-GB","potentialAction":[{"@type":"CommentAction","name":"Comment","target":["https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=18993#respond"]}]},{"@type":"WebPage","@id":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=18993","url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=18993","name":"VSEPR Theory: Octet-busting or not with trimethyl chlorine, ClMe3. - 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ClF3 is a good illustration of this theory. The standard application of VSEPR theory to this molecule is as follows: Central atom: chlorine\u2026","rel":"","context":"In "Hypervalency"","block_context":{"text":"Hypervalency","link":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?cat=7"},"img":{"alt_text":"VSEPR","src":"https:\/\/i0.wp.com\/www.ch.imperial.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2013\/07\/VSEPR.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":18993,"position":1},"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":17467,"url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=17467","url_meta":{"origin":18993,"position":2},"title":"VSEPR Theory: A closer look at bromine trifluoride, BrF3.","author":"Henry Rzepa","date":"February 14, 2017","format":false,"excerpt":"I analysed the bonding in chlorine trifluoride a few years back in terms of VSEPR theory. I noticed that several searches on this topic which led people to this post also included a query about\u00a0the differences between it and the bromine analogue. For those who posed this question, here is\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":19102,"url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=19102","url_meta":{"origin":18993,"position":3},"title":"Hypervalence and octet-expansion in trimethylene-\u03bb6-sulfane and related species.","author":"Henry Rzepa","date":"November 27, 2017","format":false,"excerpt":"Previously: \"Non-polar\" species such as SeMe6, SMe6, ClMe3, ClMe5 all revealed interesting properties for the Se-C, S-C or Cl-C \"single\" bonds. The latter two examples in particular hinted at internal structures for these single bonds, as manifested by two ELF basins for some of the bonds. Here I take a\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":19073,"url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=19073","url_meta":{"origin":18993,"position":4},"title":"Hypervalence and octet-expansion in sulfur hexafluoride.","author":"Henry Rzepa","date":"November 20, 2017","format":false,"excerpt":"Following on from discussing octet expansion in species such as SeMe6, ClMe3 and ClMe5, I felt impelled to return to SF6, often used as an icon for hypervalence. With this molecule we have twelve electrons to partition, six from sulfur and one each from six fluorines (the other six electrons\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\/11\/SF6-HIOMO-17-1024x885.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":18993,"position":5},"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":[]}],"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\/18993","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=18993"}],"version-history":[{"count":63,"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=\/wp\/v2\/posts\/18993\/revisions"}],"predecessor-version":[{"id":19061,"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=\/wp\/v2\/posts\/18993\/revisions\/19061"}],"wp:attachment":[{"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=18993"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=18993"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=18993"},{"taxonomy":"author","embeddable":true,"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fppma_author&post=18993"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}