{"id":22496,"date":"2021-01-08T13:53:46","date_gmt":"2021-01-08T18:53:46","guid":{"rendered":"https:\/\/www.bu.edu\/chemistry\/?p=22496"},"modified":"2021-01-08T13:53:46","modified_gmt":"2021-01-08T18:53:46","slug":"josh-nelson-class-of-13","status":"publish","type":"post","link":"https:\/\/www.bu.edu\/chemistry\/2021\/01\/08\/josh-nelson-class-of-13\/","title":{"rendered":"Josh Nelson (Class of ’13)"},"content":{"rendered":"

Reversible PCET and Ambient Catalytic Oxidative Alcohol Dehydrogenation by {V=O} Perfluoropinacolate Complexes<\/a><\/p>\n

A new air-stable catalyst for the oxidative dehydrogenation of benzylic alcohols under ambient conditions has been developed. The synthesis and characterization of this compound and the related monomeric and dimeric V(IV)- and V(V)-pin<\/span>F<\/sup>\u00a0(pin<\/span>F<\/sup>\u00a0= perfluoropinacolate) complexes are reported herein. Monomeric V(IV) complex (Me<\/span>4<\/sub>N)<\/span>2<\/sub>[V(O)(pin<\/span>F<\/sup>)<\/span>2<\/sub>] (<\/span>1<\/b>) and dimeric (\u03bc-O)<\/span>2<\/sub>-bridged V(V) complex (Me<\/span>4<\/sub>N)<\/span>2<\/sub>[V<\/span>2<\/sub>(O)<\/span>2<\/sub>(\u03bc-O)<\/span>2<\/sub>(pin<\/span>F<\/sup>)<\/span>2<\/sub>] (<\/span>3a<\/b>) are prepared in water under ambient conditions. Monomeric V(V) complex (Me<\/span>4<\/sub>N)[V(O)(pin<\/span>F<\/sup>)<\/span>2<\/sub>] (<\/span>2<\/b>) may be generated via chemical oxidation of\u00a0<\/span>1<\/b>\u00a0under an inert atmosphere, but dimerizes to\u00a0<\/span>3a<\/b>\u00a0upon exposure to air. Complexes\u00a0<\/span>1<\/b>\u00a0and\u00a0<\/span>2<\/b>\u00a0display a perfectly reversible V<\/span>IV\/V<\/sup>\u00a0couple at 20 mV (vs Ag\/AgNO<\/span>3<\/sub>), whereas a quasi-reversible V<\/span>IV\/V<\/sup>\u00a0couple at \u2212865 mV is found for\u00a0<\/span>3a<\/b>. Stoichiometric reactions of\u00a0<\/span>3a<\/b>\u00a0with both fluorenol and TEMPOH result in the formation of (Me<\/span>4<\/sub>N)<\/span>2<\/sub>[V<\/span>2<\/sub>(O)<\/span>2<\/sub>(\u03bc-OH)<\/span>2<\/sub>(pin<\/span>F<\/sup>)<\/span>2<\/sub>] (<\/span>4a<\/b>), which contains two V(IV) centers that display antiferromagnetic coupling. In order to structurally characterize the dinuclear anion of\u00a0<\/span>4a<\/b>, {K(18C6)}<\/span>+<\/sup>\u00a0countercations were employed, which formed stabilizing K\u00b7\u00b7\u00b7O interactions between the counterion and each terminal oxo moiety and H-bonding between the oxygen atoms of the crown ether and \u03bc-OH bridges of the dimer, resulting in {K(18C6)}<\/span>2<\/sub>[V<\/span>2<\/sub>(O)<\/span>2<\/sub>(\u03bc-OH)<\/span>2<\/sub>(pin<\/span>F<\/sup>)<\/span>2<\/sub>] (<\/span>4b<\/b>). The formal storage of H<\/span>2<\/sub>\u00a0in\u00a0<\/span>4a<\/b>\u00a0is reversible and proton-coupled electron transfer (PCET) from crystals of\u00a0<\/span>4a<\/b>\u00a0regenerates\u00a0<\/span>3a<\/b>\u00a0upon exposure to air over the course of several days. Furthermore, the reaction of\u00a0<\/span>3a<\/b>\u00a0(2%) under ambient conditions with excess fluorenol, cinnamyl alcohol, or benzyl alcohol resulted in the selective formation of fluorenone (82% conversion), cinnamaldehyde (40%), or benzaldehyde (7%), respectively, reproducing oxidative alcohol dehydrogenation (OAD) chemistry known for VO<\/span>x<\/i><\/sub>\u00a0surfaces and demonstrating, in air, the thermodynamically challenging selective oxidation of alcohols to aldehydes\/ketones.<\/span><\/p>\n","protected":false},"excerpt":{"rendered":"

Reversible PCET and Ambient Catalytic Oxidative Alcohol Dehydrogenation by {V=O} Perfluoropinacolate Complexes A new air-stable catalyst for the oxidative dehydrogenation of benzylic alcohols under ambient conditions has been developed. The synthesis and characterization of this compound and the related monomeric and dimeric V(IV)- and V(V)-pinF\u00a0(pinF\u00a0= perfluoropinacolate) complexes are reported herein. Monomeric V(IV) complex (Me4N)2[V(O)(pinF)2] (1) […]<\/p>\n","protected":false},"author":10766,"featured_media":0,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":[],"categories":[9283,9290,9275,9274],"tags":[],"_links":{"self":[{"href":"https:\/\/www.bu.edu\/chemistry\/wp-json\/wp\/v2\/posts\/22496"}],"collection":[{"href":"https:\/\/www.bu.edu\/chemistry\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.bu.edu\/chemistry\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.bu.edu\/chemistry\/wp-json\/wp\/v2\/users\/10766"}],"replies":[{"embeddable":true,"href":"https:\/\/www.bu.edu\/chemistry\/wp-json\/wp\/v2\/comments?post=22496"}],"version-history":[{"count":1,"href":"https:\/\/www.bu.edu\/chemistry\/wp-json\/wp\/v2\/posts\/22496\/revisions"}],"predecessor-version":[{"id":22498,"href":"https:\/\/www.bu.edu\/chemistry\/wp-json\/wp\/v2\/posts\/22496\/revisions\/22498"}],"wp:attachment":[{"href":"https:\/\/www.bu.edu\/chemistry\/wp-json\/wp\/v2\/media?parent=22496"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.bu.edu\/chemistry\/wp-json\/wp\/v2\/categories?post=22496"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.bu.edu\/chemistry\/wp-json\/wp\/v2\/tags?post=22496"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}