Redox Chemistry Associated with the Complexation of Vanadium(V) and Tungsten(VI) by meso-Octaethylporphyrinogen: Formation and Cleavage of Cyclopropane Units Functioning as Shuttles of Two Elec
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- 作者：Umberto Piarulli ; Euro Solari ; Carlo Floriani ; Angiola Chiesi-Villa ; and Corrado Rizzoli
- 刊名：Journal of the American Chemical Society
- 出版年：1996
- 出版时间：April 17, 1996
- 年：1996
- 卷：118
- 期：15
- 页码：3634 - 3642
- 全文大小：329K
- 年卷期：v.118,no.15(April 17, 1996)
- ISSN：1520-5126
文摘
Oxidized forms of meso-octaethylporphyrinogencontaining mono- and bis(cyclopropane) units, whichfunction as shuttles of two electrons, form from the reaction ofhigh-valent, early transition metal halides, namely[p-MeC6H4N
VCl3](2) and WOCl4, withmeso-octaethylporphyrinogen-lithium derivatives,[Et8N4Li4(THF)4](1).The reaction of 2 with 1 occurs in a 2:1ratio since the intermediate vanadium(V)-porphyrinogen complexundergoesa fast one-electron oxidation by 2 leading to[p-MeC6H4NV{Et8N4(
)}](3), which contains a vanadium(IV)-nitrene fragment bound to the two-electron, oxidized form of theporphyrinogen having a cyclopropane unit. Thislatter can be reduced using Li metal to avanadium(IV)-porphyrinogen complex,[p-MeC6H4NV(Et8N4)Li2(THF)4}](5), which was also synthesized from 1 and[(p-MeC6H4NVCl2)2](4). In the reaction of WOCl4, we foundthatthe tungsten(VI)-porphyrinogen complex forms first and is ableto oxidize the excess of 1, to give[Et8N4()Li2(THF)2] (8) or the[Et8N4()2Li(THF)]+cation (9B), depending on the stoichiometric ratio. Theformer formsalong with[Et8N4W=OLi(THF)4](7) when a WOCl4:1 ratio of 2:3 wasused. In the case of a 4:5 ratio, 9B wasisolated as a countercation of[Et8N4W=O]- (9A).The bis(cyclopropane) form of porphyrinogen becomesavailableby reacting 9 with NaBPh4, thus forming[Et8N4()2Li]+BPh4-(11). The lithium derivatives, 8 and11, are theoxidized forms of porphyrinogen available for synthesis. Thetungstenyl anion in 7 can be converted into theinorganicester [Et8N4WOC(O)Ph](12) by reacting it with PhCOCl.
VCl3](2) and WOCl4, withmeso-octaethylporphyrinogen-lithium derivatives,[Et8N4Li4(THF)4](1).The reaction of 2 with 1 occurs in a 2:1ratio since the intermediate vanadium(V)-porphyrinogen complexundergoesa fast one-electron oxidation by 2 leading to[p-MeC6H4NV{Et8N4()}](3), which contains a vanadium(IV)-nitrene fragment bound to the two-electron, oxidized form of theporphyrinogen having a cyclopropane unit. Thislatter can be reduced using Li metal to avanadium(IV)-porphyrinogen complex,[p-MeC6H4NV(Et8N4)Li2(THF)4}](5), which was also synthesized from 1 and[(p-MeC6H4NVCl2)2](4). In the reaction of WOCl4, we foundthatthe tungsten(VI)-porphyrinogen complex forms first and is ableto oxidize the excess of 1, to give[Et8N4()Li2(THF)2] (8) or the[Et8N4()2Li(THF)]+cation (9B), depending on the stoichiometric ratio. Theformer formsalong with[Et8N4W=OLi(THF)4](7) when a WOCl4:1 ratio of 2:3 wasused. In the case of a 4:5 ratio, 9B wasisolated as a countercation of[Et8N4W=O]- (9A).The bis(cyclopropane) form of porphyrinogen becomesavailableby reacting 9 with NaBPh4, thus forming[Et8N4()2Li]+BPh4-(11). The lithium derivatives, 8 and11, are theoxidized forms of porphyrinogen available for synthesis. Thetungstenyl anion in 7 can be converted into theinorganicester [Et8N4WOC(O)Ph](12) by reacting it with PhCOCl.