Redox-Switched Complexation/Decomplexation of K+ and Cs+ by Molecular Cyanometalate Boxes
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- 作者：Julie L. Boyer ; Maya Ramesh ; Haijun Yao ; Thomas B. Rauchfuss ; Scott R. Wilson
- 刊名：Journal of the American Chemical Society
- 出版年：2007
- 出版时间：February 21, 2007
- 年：2007
- 卷：129
- 期：7
- 页码：1931 - 1936
- 全文大小：168K
- 年卷期：v.129,no.7(February 21, 2007)
- ISSN：1520-5126
文摘
The reaction of [N(PPh3)2][CpCo(CN)3] and [Cb*Co(NCMe)3]PF6 (Cb* = C4Me4) in the presenceof K+ afforded {K
[CpCo(CN)3]4[Cb*Co]4}PF6, [KCo8]PF6. IR, NMR, ESI-MS indicate that [KCo8]PF6 is ahigh-symmetry molecular box containing a potassium ion at its interior. The analogous heterometallic cage{K[Cp*Rh(CN)3]4[Cb*Co]4}PF6 ([KRh4Co4]PF6) was prepared similarly via the condensation of K[Cp*Rh(CN)3] and [Cb*Co(NCMe)3]PF6. Crystallographic analysis confirmed the structure of [KCo8]PF6. The cyanideligands are ordered, implying that no Co-CN bonds are broken upon cage formation and ion complexation.Eight Co-CN-Co edges of the box bow inward toward the encapsulated K+, and the remaining four 
-CNligands bow outward. MeCN solutions of [KCo8]+ and [KRh4Co4]+ were found to undergo ion exchangewith Cs+ to give [CsCo8]+ and [CsRh4Co4]+, both in quantitative yields. Labeling experiments involving[(MeC5H4)Co(CN)3]- demonstrated that Cs+-for-K+ ion exchange is accompanied by significant fragmentation. Ion exchange of NH4+ with [KCo8]+ proceeds to completion in THF solution, but in MeCN solution, theexclusive products were [Cb*Co(NCMe)3]PF6 and the poorly soluble salt NH4CpCo(CN)3. The lability ofthe NH4+-containing cage was also indicated by the rapid exchange of the acidic protons in [NH4Co8]+.Oxidation of [MCo8]+ with 4 equiv of FcPF6 produced paramagnetic (S = 4/2) [Co8]4+, releasing Cs+ or K+.The oxidation-induced dissociation of M+ from the cages is chemically reversed by treatment of [Co8]4+and CsOTf with 4 equiv of Cp2Co. Cation recognition by [Co8] and [Rh4Co4] cages was investigated.Electrochemical measurements indicated that E1/2(Cs+) - E1/2(K+) ~ 0.08 V for [MCo8]+.
[CpCo(CN)3]4[Cb*Co]4}PF6, [KCo8]PF6. IR, NMR, ESI-MS indicate that [KCo8]PF6 is ahigh-symmetry molecular box containing a potassium ion at its interior. The analogous heterometallic cage{K[Cp*Rh(CN)3]4[Cb*Co]4}PF6 ([KRh4Co4]PF6) was prepared similarly via the condensation of K[Cp*Rh(CN)3] and [Cb*Co(NCMe)3]PF6. Crystallographic analysis confirmed the structure of [KCo8]PF6. The cyanideligands are ordered, implying that no Co-CN bonds are broken upon cage formation and ion complexation.Eight Co-CN-Co edges of the box bow inward toward the encapsulated K+, and the remaining four -CNligands bow outward. MeCN solutions of [KCo8]+ and [KRh4Co4]+ were found to undergo ion exchangewith Cs+ to give [CsCo8]+ and [CsRh4Co4]+, both in quantitative yields. Labeling experiments involving[(MeC5H4)Co(CN)3]- demonstrated that Cs+-for-K+ ion exchange is accompanied by significant fragmentation. Ion exchange of NH4+ with [KCo8]+ proceeds to completion in THF solution, but in MeCN solution, theexclusive products were [Cb*Co(NCMe)3]PF6 and the poorly soluble salt NH4CpCo(CN)3. The lability ofthe NH4+-containing cage was also indicated by the rapid exchange of the acidic protons in [NH4Co8]+.Oxidation of [MCo8]+ with 4 equiv of FcPF6 produced paramagnetic (S = 4/2) [Co8]4+, releasing Cs+ or K+.The oxidation-induced dissociation of M+ from the cages is chemically reversed by treatment of [Co8]4+and CsOTf with 4 equiv of Cp2Co. Cation recognition by [Co8] and [Rh4Co4] cages was investigated.Electrochemical measurements indicated that E1/2(Cs+) - E1/2(K+) ~ 0.08 V for [MCo8]+.