{"id":17710,"date":"2017-03-16T17:22:19","date_gmt":"2017-03-16T17:22:19","guid":{"rendered":"http:\/\/www.ch.imperial.ac.uk\/rzepa\/blog\/?p=17710"},"modified":"2017-03-16T17:22:19","modified_gmt":"2017-03-16T17:22:19","slug":"how-does-silane-invert-its-configuration","status":"publish","type":"post","link":"https:\/\/rzepa.net\/blog\/2017\/03\/16\/how-does-silane-invert-its-configuration\/","title":{"rendered":"How does silane invert (its configuration)?"},"content":{"rendered":"<p>In the <a href=\"http:\/\/www.ch.imperial.ac.uk\/rzepa\/blog\/?p=17702\">previous post<\/a>, I found intriguing the mechanism by which methane (CH<sub>4<\/sub>) inverts by transposing two of its hydrogens. Here I take a look at silane, SiH<sub>4<\/sub>.<\/p>\n<p>It appears it is a three-stage process! Firstly, silane eliminates molecular hydrogen to form a molecular complex between H<sub>2\u00a0<\/sub>and SiH<sub>2<\/sub> (DOI:\u00a0<a href=\"https:\/\/doi.org\/10.14469\/hpc\/2290\">10.14469\/hpc\/2290<\/a>). The barrier (~60 kcal\/mol) is very much lower than with methane.<\/p>\n<p><img decoding=\"async\" class=\"aligncenter size-full wp-image-17715\" src=\"http:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2017\/03\/SiH4-elim.gif\" alt=\"\" width=\"450\" \/><a href=\"http:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2017\/03\/gaussian-78_tot_ener.svg\"><img decoding=\"async\" class=\"aligncenter size-large wp-image-17718\" src=\"http:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2017\/03\/gaussian-78_tot_ener.svg\" alt=\"\" width=\"450\" \/><\/a><a href=\"http:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2017\/03\/gaussian-78_tot_ener.svg\"><img loading=\"lazy\" decoding=\"async\" class=\"aligncenter size-large wp-image-17717\" src=\"http:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2017\/03\/gaussian-78_tot_ener.svg\" alt=\"\" width=\"1\" height=\"1\" \/><\/a><\/p>\n<p>The H<sub>2<\/sub> component of this complex then rotates (DOI: <a href=\"https:\/\/doi.org\/10.14469\/hpc\/2289\">10.14469\/hpc\/2289<\/a>) transposing atoms 1 and 2. The barrier for this process is tiny (~4 kcal\/mol).<\/p>\n<p><img decoding=\"async\" class=\"aligncenter size-full wp-image-17711\" src=\"http:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2017\/03\/SiH4-rot.gif\" alt=\"\" width=\"450\" \/><img decoding=\"async\" class=\"aligncenter size-large wp-image-17709\" src=\"http:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2017\/03\/gaussian-27_tot_ener.svg\" alt=\"\" width=\"450\" \/><\/p>\n<p>Finally, the rotated H<sub>2<\/sub>\/SiH<sub>2<\/sub> complex goes back to silane by the first route, but now with the two hydrogens transposed.<\/p>\n<p>So this inversion is a<strong><span style=\"color: #ff0000;\"> stepwise process<\/span><\/strong> in contrast to methane which was<strong><span style=\"color: #ff0000;\"> concerted<\/span><\/strong>, albeit with &#8220;frustrated&#8221; elimination of hydrogen. Again a little molecule can show us so much chemistry, in this case also illustrating the <a href=\"http:\/\/www.ch.imperial.ac.uk\/rzepa\/blog\/?p=6977\">avoidance of a Woodward-Hoffmann forbidden cheletropic elimination<\/a> by desymmetrisation.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>In the previous post, I found intriguing the mechanism by which methane (CH4) inverts by transposing two of its hydrogens. Here I take a look at silane, SiH4. It appears it is a three-stage process! Firstly, silane eliminates molecular hydrogen to form a molecular complex between H2\u00a0and SiH2 (DOI:\u00a010.14469\/hpc\/2290). The barrier (~60 kcal\/mol) is very [&hellip;]<\/p>\n","protected":false},"author":2,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[13],"tags":[542,1267,1628,2233,2234],"class_list":["post-17710","post","type-post","status-publish","format-standard","hentry","category-reaction-mechanism-2","tag-chemistry","tag-industrial-gases","tag-methane","tag-sih2-complex","tag-silanes"],"_links":{"self":[{"href":"https:\/\/rzepa.net\/blog\/wp-json\/wp\/v2\/posts\/17710","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/rzepa.net\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/rzepa.net\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/rzepa.net\/blog\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/rzepa.net\/blog\/wp-json\/wp\/v2\/comments?post=17710"}],"version-history":[{"count":0,"href":"https:\/\/rzepa.net\/blog\/wp-json\/wp\/v2\/posts\/17710\/revisions"}],"wp:attachment":[{"href":"https:\/\/rzepa.net\/blog\/wp-json\/wp\/v2\/media?parent=17710"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/rzepa.net\/blog\/wp-json\/wp\/v2\/categories?post=17710"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/rzepa.net\/blog\/wp-json\/wp\/v2\/tags?post=17710"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}