{"id":22971,"date":"2020-11-07T12:13:33","date_gmt":"2020-11-07T12:13:33","guid":{"rendered":"https:\/\/www.ch.imperial.ac.uk\/rzepa\/blog\/?p=22971"},"modified":"2020-11-07T12:13:33","modified_gmt":"2020-11-07T12:13:33","slug":"a-new-example-of-a-quadruple-bond-from-carbon-to-fe","status":"publish","type":"post","link":"https:\/\/www.rzepa.net\/blog\/?p=22971","title":{"rendered":"A new example of a quadruple bond from carbon – to Fe."},"content":{"rendered":"
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Way back in 2010, I was writing<\/a> about an experience I had just had during an organic chemistry tutorial, which morphed into speculation as to whether a carbon atom might sustain a quadruple bond to nitrogen. A decade on, and possibly approaching 100 articles by many authors on the topic, quadruple bonds to carbon continue to fascinate. Now an article as appeared[1]<\/a><\/span> repeating this speculation for a carbon to iron quadruple bond, in the very simple species C\u2a78Fe(CO)3<\/sub>. This is particularly exciting because of the very real prospect of synthesising this species and perchance getting a crystal structure (something not possible with most of the other quadruply bonded carbon systems studied to date).<\/p>\n

They authors report[1]<\/a><\/span> that this sytem is well described by a single-configurational wavefunction and hence that a M062X\/Def2-TZVPP calculation is a good description of the bonding. In the article you will find the valence molecular orbitals shown, which by their nature show a lot of delocalisation. Because the more localised NBOs are not shown in the article, I illustrate them here, as 3D rotatable models. The DOI for the calculation can be found at\u00a010.14469\/hpc\/7537<\/a>.<\/p>\n\n\n\n\n\n\n\n
CFe(CO)3<\/sub><\/th>\n<\/tr>\n
NBO 37 π<\/th>\nNBO 36 π<\/th>\n<\/tr>\n
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Click to view 3D model of NBO 37<\/p><\/div>\n<\/td>\n

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Click to view 3D model of NBO 36<\/p><\/div>\n<\/td>\n<\/tr>\n

NBO 33 σ<\/th>\nNBO 23 σ<\/th>\n<\/tr>\n
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Click to view 3D model of NBO 33<\/p><\/div>\n<\/td>\n

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Click to view 3D model of NBO 23<\/p><\/div>\n<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

These NBOs show very clearly that the two higher energy orbitals are orthogonal \u03c0-bonds to carbon from Fe and the two lower energy orbitals are both \u03c3-bonds to carbon from Fe. Exactly the same picture appears for C2<\/sub>, which has been often mentioned<\/a> on this blog.<\/p>\n

All that remains is that some inspired synthetic chemist sets out to make C\u2a78Fe(CO)3<\/sub> and to report back on its properties. I fancy the last has not yet been heard about quadruple bonds to carbon!<\/p>\n

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Postscript:<\/b> Here are the analogous orbitals for the species N\u2a78Mn(CO)3<\/sub> to illustrate their evolution across an isoelectronic series.<\/p>\n\n\n\n\n\n\n\n
NMn(CO)3<\/sub><\/th>\n<\/tr>\n
NBO 35<\/th>\nNBO 34<\/th>\n<\/tr>\n
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Click to view 3D model of NBO 35<\/p><\/div>\n<\/td>\n

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Click to view 3D model of NBO 34<\/p><\/div>\n<\/td>\n<\/tr>\n

NBO 33<\/th>\nNBO 20<\/th>\n<\/tr>\n
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Click to view 3D model of NBO 33<\/p><\/div>\n<\/td>\n

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Click to view 3D model of NBO 20<\/p><\/div>\n<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

NBO 33 (the higher in energy of the two σ-type bonds) has an interesting structure. Here it is at a slightly lower threshold:<\/p>\n

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Click to view 3D model of NBO 33 for NMn(CO)3 at threshold 0.015au<\/p><\/div>\n

It has an inner compact σ-bond running along the axis of the bond and an outer “wrap” of different phase. A two layer σ-bond if you like!<\/p>\n

References<\/h2>\n
  1. A.J. Kalita, S.S. Rohman, C. Kashyap, S.S. Ullah, and A.K. Guha, \"Transition metal carbon quadruple bond: viability through single electron transmutation\", Physical Chemistry Chemical Physics<\/i>, vol. 22, pp. 24178-24180, 2020. https:\/\/doi.org\/10.1039\/d0cp03436c<\/a>\n\n<\/li>\n<\/ol>\n\n<\/div> ","protected":false},"excerpt":{"rendered":"

    Way back in 2010, I was writing about an experience I had just had during an organic chemistry tutorial, which morphed into speculation as to whether a carbon atom might sustain a quadruple bond to nitrogen. A decade on, and possibly approaching 100 articles by many authors on the topic, quadruple bonds to carbon continue […]<\/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":[6],"tags":[1526],"class_list":["post-22971","post","type-post","status-publish","format-standard","hentry","category-interesting-chemistry","tag-interesting-chemistry"],"jetpack_publicize_connections":[],"jetpack_featured_media_url":"","jetpack_sharing_enabled":true,"jetpack_shortlink":"https:\/\/wp.me\/p1gPyz-5Yv","jetpack_likes_enabled":true,"_links":{"self":[{"href":"https:\/\/www.rzepa.net\/blog\/index.php?rest_route=\/wp\/v2\/posts\/22971","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=22971"}],"version-history":[{"count":0,"href":"https:\/\/www.rzepa.net\/blog\/index.php?rest_route=\/wp\/v2\/posts\/22971\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.rzepa.net\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=22971"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.rzepa.net\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=22971"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.rzepa.net\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=22971"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}