Redox-Switchable Chiral Anions and Cations Based on Heteroatom-Fused Biferrocenes

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• 作者：Jiawei Chen ; Didier A. Murillo Parra ; Roger A. Lalancette ; Frieder J盲kle
• 刊名：Organometallics
• 出版年：2015
• 出版时间：September 14, 2015
• 年：2015
• 卷：34
• 期：17
• 页码：4323-4330
• 全文大小：454K
• ISSN：1520-6041

文摘

A new class of planar chiral heteroatom-bridged biferrocene species was prepared using (pR,pR,S_S,S_S)-2,2鈥?bis(p-tolylsulfinyl)-1,1鈥?biferrocene (pR,pR,S_S,S_S)-2 as a readily accessible precursor. Initially, one of the sulfinate groups in compound 2 is replaced with a trimethylstannyl or dimesitylboryl group. Replacement of the second sulfinate group with t-BuLi then results in cyclization to give the Me₂Sn-bridged species (pS,pS)-4Sn and the Mes₂B-bridged borate anion [(pS,pS)-4B]^{鈭?/sup>. The products are redox active, as cyclic and square wave voltammetry data of (pS,pS)-4Sn and [Li(12-c-4)₂][(pS,pS)-4B] reveal two separate reversible oxidation events. The mixed-valent species [(pS,pS)-4Sn]+ and (pS,pS)-4B can also be obtained by chemical oxidation with AgPF₆ or by simple exposure to air, respectively. A comparison of X-ray crystal structures reveals that the oxidized (mixed-valent) species contain distinct Fe(II) and Fe(III) sites, but UV鈥搗isible鈥揘IR spectra display IVCT bands at ca. 4000 and 5000 cm鈥?, indicative of electronic coupling in solution. All compounds are obtained in enantiomerically pure form, suggesting potential use as switchable chiral anions and cations.}