{"id":19194,"date":"2017-12-08T14:48:51","date_gmt":"2017-12-08T14:48:51","guid":{"rendered":"http:\/\/www.ch.imperial.ac.uk\/rzepa\/blog\/?p=19194"},"modified":"2017-12-08T14:48:51","modified_gmt":"2017-12-08T14:48:51","slug":"identification-of-a-simplest-hypervalent-hydrogen-fluoride-anion","status":"publish","type":"post","link":"https:\/\/www.rzepa.net\/blog\/?p=19194","title":{"rendered":"Identification of a simplest hypervalent hydrogen fluoride anion."},"content":{"rendered":"
\n

An article with the title shown above in part recently appeared.[1]<\/a><\/span> Given the apparent similarity of HF1-<\/sup> to CH3<\/sub>F1-<\/sup> and CH3<\/sub>F2-<\/sup>, the latter of which I introduced on this blog previously,\u00a0<\/a>I thought it of interest to apply my analysis to HF1-<\/sup>.<\/p>\n

The authors[1]<\/a><\/span> conclude that “the F atom of HF\u2212<\/sup> is negative and hypervalent and the bonding is more covalent than ionic<\/em>“.\u00a0So, firstly an NBO analysis. Shown below is the singly occupied NBO (\u03c9B97XD\/Def2-TZVPPD calculation, FAIR data DOI: 10.14469\/hpc\/3274)<\/a><\/p>\n

\"\"<\/p>\n

The nature of this orbital is that most of it is located beyond the hydrogen and a node is apparent between the F and H (it is H-F antibonding). The Wiberg bond index for both H and F is 0.48, as is the F-H bond order. This matches with the observation of one electron in an orbital which is H-F antibonding. NBO analysis also indicates that the atomic orbital contributions to F[core]2S(1.93)2p(5.77)3S(0.05<\/span>)3p(0.04<\/span>)3d(0.01) and H 1S(0.96)2S(0.12<\/span>)2p(0.10<\/span>) show modest Rydberg character on the hydrogen, less on the fluorine. By this criterion, it is the hydrogen and not the fluorine that is hypervalent!<\/p>\n

Next, the ELF analysis (respectively FAIR data DOI: DFT\u00a010.14469\/hpc\/3377<\/a>\u00a0 and CASSCF(7,8)\u00a010.14469\/hpc\/3394<\/a>).\u00a0<\/p>\n\n\n\n\n
DFT<\/th>\nCASSCF(7,8)<\/th>\n<\/tr>\n
\"\"<\/td>\n\"\"<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

Both these methods reveal a monosynaptic ELF basin located away from the H, with an integration of about 1 electron. The F lone pairs form a torus around the F and the total of electrons around the fluorine is <8. So again no evidence from ELF that the fluorine is hypervalent.<\/p>\n

In fact this analysis resembles one feature of CLi6<\/a>. With nominally 12e apparently contributing to the shared C-Li shell, CLi6<\/sub> was described as hypervalent.[2]<\/a><\/span> In fact ~3e of these are “expelled” from the shared C-Li regions into Li-Li regions, where they contribute only to lithium valency and not to the carbon valency. With\u00a0HF1-<\/sup>, the additional electron apparently responsible for the hypervalency <\/i>contributes only to the H, but not<\/strong> to the F valencies. With\u00a0CH3<\/sub>F2-<\/sup>, the two injected electrons do appear to contribute to the C-F bond, making it a true hyperbond<\/strong>.<\/p>\n

So based on the above, I cannot entirely agree with the assertion that “the F atom of HF\u2212<\/sup> is negative and hypervalent”<\/em>[1]<\/a><\/span>, but I might suggest that something more unusual is happening, the hydrogen<\/strong> is (mildly) hypervalent!\u00a0<\/p>\n

References<\/h2>\n
  1. M. Liu, H. Chen, C. Chin, T. Huang, Y. Chen, and Y. Wu, \"Identification of a Simplest Hypervalent Hydrogen Fluoride Anion in Solid Argon\", Scientific Reports<\/i>, vol. 7, 2017. https:\/\/doi.org\/10.1038\/s41598-017-02687-z<\/a>\n\n<\/li>\n
  2. H. Kudo, \"Observation of hypervalent CLi6 by Knudsen-effusion mass spectrometry\", Nature<\/i>, vol. 355, pp. 432-434, 1992. https:\/\/doi.org\/10.1038\/355432a0<\/a>\n\n<\/li>\n<\/ol>\n\n<\/div> ","protected":false},"excerpt":{"rendered":"

    An article with the title shown above in part recently appeared. Given the apparent similarity of HF1- to CH3F1- and CH3F2-, the latter of which I introduced on this blog previously,\u00a0I thought it of interest to apply my analysis to HF1-. The authors conclude that “the F atom of HF\u2212 is negative and hypervalent and […]<\/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,"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":[5],"tags":[1525],"class_list":["post-19194","post","type-post","status-publish","format-standard","hentry","category-hypervalency","tag-hypervalency"],"jetpack_publicize_connections":[],"jetpack_featured_media_url":"","jetpack_sharing_enabled":true,"jetpack_shortlink":"https:\/\/wp.me\/p1gPyz-4ZA","jetpack_likes_enabled":true,"_links":{"self":[{"href":"https:\/\/www.rzepa.net\/blog\/index.php?rest_route=\/wp\/v2\/posts\/19194","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.rzepa.net\/blog\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.rzepa.net\/blog\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.rzepa.net\/blog\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.rzepa.net\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=19194"}],"version-history":[{"count":0,"href":"https:\/\/www.rzepa.net\/blog\/index.php?rest_route=\/wp\/v2\/posts\/19194\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.rzepa.net\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=19194"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.rzepa.net\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=19194"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.rzepa.net\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=19194"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}