{"id":17483,"date":"2017-02-15T14:08:27","date_gmt":"2017-02-15T14:08:27","guid":{"rendered":"http:\/\/www.ch.imperial.ac.uk\/rzepa\/blog\/?p=17483"},"modified":"2017-06-09T13:30:54","modified_gmt":"2017-06-09T12:30:54","slug":"the-h4-2-dication-and-its-bonding","status":"publish","type":"post","link":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=17483","title":{"rendered":"The H4 (2+) dication and its bonding."},"content":{"rendered":"
\n

This post arose from a comment<\/a> attached to the post on Na2<\/sub>He<\/a>\u00a0and relating to peculiar and rare topological features of the electron density in molecules called non-nuclear attractors. This set me thinking about other molecules that might exhibit this and one of these is shown below.<\/p>\n

The topology of the electron density is described by just four basic types, designed formally by the notation [3,-3], [3,-1], [3,1] and [3,3] and more colloquially by the terms nuclear attractor<\/strong> (NNA<\/strong>), line (<\/strong>or bond)<\/strong> critical point, a\u00a0ring<\/strong> critical point and a\u00a0cage<\/strong> critical point respectively. Mostly, the nuclear critical points coincide exactly with the actual nuclear positions, but more rarely these points are not found centered at a nucleus. It was such an NNA that was suggested<\/a>\u00a0as a comment on the\u00a0post on Na2<\/sub>He<\/a>. There I\u00a0replied<\/a>\u00a0that another example of an\u00a0NNA is to be found in H3<\/sub>+<\/sup> and so its a short step to take a look at H4<\/sub>2+<\/sup> in a tetrahedral arrangement (DOI: 10.14469\/hpc\/2165<\/a>).\u00a0Since only two electrons are available for bonding, it is tempting to represent it as below, with dashed partial bonds connnecting the six edges of the tetrahedron and is associated with real normal vibrational modes; \u03bd 416, 1490 and 1861 cm-1<\/sup>. A brief search on Scifinder, which appears to reference this species as\u00a0hydrogen, ion (H4<\/sub>2+<\/sup>),\u00a0<\/em>does not identify any publications associated with it (there are studies on H4<\/sub>1+<\/sup>\u00a0however); if any reader here knows of any discussion please alert us!<\/p>\n

\"\"<\/p>\n

Analysing the density however gives a different result. A NNA is located at the centre of the tetrahedron and a line (bond) critical point connects this to each of the four hydrogen nuclei. This result is similar to the obtained for H3<\/sub>+<\/sup>. It is rather odd that these non-nuclear attractors have not entered into the vocabulary used to describe the bonding in simple molecules, but this picture is certainly different from the more empirical dashed lines between the four nuclei that one is instinctively drawn to use (above).<\/p>\n

\"\"<\/p>\n

The ELF analysis (performed using multiWFN) is more interesting. The nuclear basins associated with the hydrogens reveal each has 0.425e, but the central one (green below) has its own basin with 0.301e.\u00a0<\/p>\n

\"\"<\/p>\n

The NICS value associated with the non-nuclear attractor\u00a0is -27 ppm, which is indicative of strong spherical aromaticity<\/a>.\u2021<\/sup><\/p>\n

All of which goes to show that even the simplest of molecular species may still have properties that are unexpected or certainly not well-known!<\/p>\n

\n

\u2021<\/sup>The H3<\/sub>+<\/sup> species also has a non-nuclear attractor with a NICS value of -33ppm, this time two dimensionally aromatic (DOI:\u00a010.14469\/hpc\/2653<\/a>).<\/p>\n\n<\/div> ","protected":false},"excerpt":{"rendered":"

This post arose from a comment attached to the post on Na2He\u00a0and relating to peculiar and rare topological features of the electron density in molecules called non-nuclear attractors. This set me thinking about other molecules that might exhibit this and one of these is shown below. The topology of the electron density is described by […]<\/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":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},"jetpack_post_was_ever_published":false},"categories":[4],"tags":[2005,2007,1395,1513,2006,1960,1966,1871,1872,1512],"ppma_author":[2661],"class_list":["post-17483","post","type-post","status-publish","format-standard","hentry","category-interesting-chemistry","tag-attractor","tag-brief-search","tag-chemistry","tag-electron","tag-electron-density","tag-hydrogen","tag-molecule","tag-nature","tag-physics","tag-quantum-chemistry"],"yoast_head":"\nThe H4 (2+) dication and its bonding. - 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=17483\" \/>\n<meta property=\"og:locale\" content=\"en_GB\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"The H4 (2+) dication and its bonding. - Henry Rzepa's Blog\" \/>\n<meta property=\"og:description\" content=\"This post arose from a comment attached to the post on Na2He\u00a0and relating to peculiar and rare topological features of the electron density in molecules called non-nuclear attractors. This set me thinking about other molecules that might exhibit this and one of these is shown below. The topology of the electron density is described by […]\" \/>\n<meta property=\"og:url\" content=\"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=17483\" \/>\n<meta property=\"og:site_name\" content=\"Henry Rzepa's Blog\" \/>\n<meta property=\"article:published_time\" content=\"2017-02-15T14:08:27+00:00\" \/>\n<meta property=\"article:modified_time\" content=\"2017-06-09T12:30:54+00:00\" \/>\n<meta property=\"og:image\" content=\"http:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2017\/02\/049-1009x1024.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=\"2 minutes\" \/>\n<!-- \/ Yoast SEO plugin. -->","yoast_head_json":{"title":"The H4 (2+) dication and its bonding. - 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=17483","og_locale":"en_GB","og_type":"article","og_title":"The H4 (2+) dication and its bonding. - Henry Rzepa's Blog","og_description":"This post arose from a comment attached to the post on Na2He\u00a0and relating to peculiar and rare topological features of the electron density in molecules called non-nuclear attractors. 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The topology of the electron density is described by […]","og_url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=17483","og_site_name":"Henry Rzepa's Blog","article_published_time":"2017-02-15T14:08:27+00:00","article_modified_time":"2017-06-09T12:30:54+00:00","og_image":[{"url":"http:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2017\/02\/049-1009x1024.jpg","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=17483#article","isPartOf":{"@id":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=17483"},"author":{"name":"Henry Rzepa","@id":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/#\/schema\/person\/2b40f7b9c872a4dc1547e040a11b6281"},"headline":"The H4 (2+) dication and its bonding.","datePublished":"2017-02-15T14:08:27+00:00","dateModified":"2017-06-09T12:30:54+00:00","mainEntityOfPage":{"@id":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=17483"},"wordCount":434,"commentCount":11,"image":{"@id":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=17483#primaryimage"},"thumbnailUrl":"http:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2017\/02\/049-1009x1024.jpg","keywords":["Attractor","brief search","Chemistry","Electron","Electron density","Hydrogen","Molecule","Nature","Physics","Quantum chemistry"],"articleSection":["Interesting chemistry"],"inLanguage":"en-GB","potentialAction":[{"@type":"CommentAction","name":"Comment","target":["https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=17483#respond"]}]},{"@type":"WebPage","@id":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=17483","url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=17483","name":"The H4 (2+) dication and its bonding. - 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One specific example of this need is for the molecule shown below. This is the so-called Pirkle Reagent and is much used to help resolve the two enantiomers of a racemic\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":"The Pirkle reagent","src":"https:\/\/i0.wp.com\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2009\/04\/pirkle.jpg?resize=350%2C200","width":350,"height":200},"classes":[]},{"id":4987,"url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=4987","url_meta":{"origin":17483,"position":1},"title":"Are close H…H contacts bonds?","author":"Henry Rzepa","date":"October 7, 2011","format":false,"excerpt":"The properties of electrons are studied by both chemists and physicists. At the boundaries of these two disciplines, sometimes interesting differences in interpretation emerge. One of the most controversial is that due to Bader (for a recent review, see DOI: 10.1021\/jp102748b) a physicist who brought the mathematical rigor of electronic\u2026","rel":"","context":"In "General"","block_context":{"text":"General","link":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?cat=1"},"img":{"alt_text":"","src":"https:\/\/i0.wp.com\/www.ch.imperial.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2011\/10\/cis-butene2.jpg?resize=350%2C200","width":350,"height":200},"classes":[]},{"id":14272,"url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=14272","url_meta":{"origin":17483,"position":2},"title":"Electrides (aka solvated electrons).","author":"Henry Rzepa","date":"July 8, 2015","format":false,"excerpt":"Peter Edwards has just given the 2015 Hofmann lecture here at Imperial on the topic of solvated electrons. An organic chemist knows this species as \"e-\" and it occurs in ionic compounds known as electrides; chloride = the negative anion of a chlorine atom, hence electride = the negative anion\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":17498,"url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=17498","url_meta":{"origin":17483,"position":3},"title":"More tetrahedral fun. Spherical aromaticity (and other oddities) in N4 and C4 systems?","author":"Henry Rzepa","date":"March 2, 2017","format":false,"excerpt":"The thread thus far. The post about Na2He introduced the electride anionic counter-ion to Na+ as corresponding topologically to a rare feature known as a non-nuclear attractor. This prompted speculation about other systems with such a feature, and the focus shifted to a tetrahedral arrangement of four hydrogen atoms as\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":811,"url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=811","url_meta":{"origin":17483,"position":4},"title":"Capturing penta-coordinate carbon! (Part 2).","author":"Henry Rzepa","date":"September 23, 2009","format":false,"excerpt":"In this follow-up to the previous post, I will try to address the question what is the nature of the bonds in penta-coordinate carbon? This is a difficult question to answer with any precision, largely because our concept of a bond derives from trying to define what the properties of\u2026","rel":"","context":"In "Hypervalency"","block_context":{"text":"Hypervalency","link":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?cat=7"},"img":{"alt_text":"The Sn2 transition state","src":"https:\/\/i0.wp.com\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2009\/09\/sn2.jpg?resize=350%2C200","width":350,"height":200},"classes":[]},{"id":8048,"url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=8048","url_meta":{"origin":17483,"position":5},"title":"Trimethylenemethane Ruthenium benzene","author":"Henry Rzepa","date":"October 17, 2012","format":false,"excerpt":"Every once in a while, one encounters a molecule which instantly makes an interesting point. Thus Ruthenium is ten electrons short of completing an 18-electron shell, and it can form a complex with benzene on one face and a ligand known as trimethylenemethane on the other. This four-carbon molecule has\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":"https:\/\/i0.wp.com\/www.ch.imperial.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2012\/10\/JODLIX.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\/17483","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=17483"}],"version-history":[{"count":12,"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=\/wp\/v2\/posts\/17483\/revisions"}],"predecessor-version":[{"id":18513,"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=\/wp\/v2\/posts\/17483\/revisions\/18513"}],"wp:attachment":[{"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=17483"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=17483"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=17483"},{"taxonomy":"author","embeddable":true,"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fppma_author&post=17483"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}