Carbonate binding to copper(ii) in solution: mixed-ligand complex formation and its application to the isolation and separation of the three isomers of [Cu(bpp)(H2O)][ClO4]2 [bpp = 2,6-bis(pyrrolidin-2-yl)pyridine]
作者:Klaus Bernauer、Amel Cabort、Nathalie Guicher、Helen Stoeckli-Evans、Georg Süss-Fink
DOI:10.1039/b111501b
日期:2002.4.26
The binding of the carbonate anion to [Cu(meso-bpp)(H2O)]2+ and rac-[Cu(bpp)(H2O)]2+ [bpp = 2,6-bis(pyrrolidin-2-yl)pyridine] in aqueous solution has been investigated. Formation constants of the carbonato complexes [Cu(meso-bpp)(CO3)] and rac-[Cu(bpp)(CO3)] (1.02 × 103 M−1 and 1.77 × 103 M−1, respectively, μ
= 0.70 M) have been calculated from spectrophotometric measurements. The formation of these Cu2+ complexes can also be used for an improved synthesis and an easy isolation of the three diastereoisomers of bpp. The mixture of [Cu(meso-bpp)(H2O)]2+ and rac-[Cu(bpp)(H2O)]2+ is separated by elution from SP Sephadex C-25, either as hydroxo or carbonato derivatives. rac-[Cu(bpp)(H2O)]2+
is then resolved into the enantiomers [Cu(S,S-bpp)(H2O)]2+ and [Cu(R,R-bpp)(H2O)]2+, again on SP Sephadex C-25, by means of L-(+)-tartrate as chiral eluent. The three stereoisomers, meso-bpp, (S,S)-bpp and (R,R)-bpp are liberated from the corresponding copper(II) complexes by ligand displacement using trans-1,2-diaminocyclohexane-N,N,N′,N′-tetraacetic acid (H4cdta). The structure of the meso isomer was solved by a single crystal X-ray analysis using the perchlorate salt [meso-bppH2][ClO4]2·2H2O.
已在水溶液中研究了碳酸根阴离子与[Cu(meso-bpp)(H2O)]²⁺和rac-[Cu(bpp)(H2O)]²⁺的结合(bpp = 2,6-bis(pyrrolidin-2-yl)pyridine)。通过光谱测量计算得到了碳酸复合物[Cu(meso-bpp)(CO3)]和rac-[Cu(bpp)(CO3)]的形成常数分别为1.02 × 10³ M⁻¹和1.77 × 10³ M⁻¹(μ = 0.70 M)。这些Cu²⁺复合物的形成也可用于改善bpp三个非对映异构体的合成和简易分离。将[Cu(meso-bpp)(H2O)]²⁺与rac-[Cu(bpp)(H2O)]²⁺的混合物通过SP Sephadex C-25洗脱分离,作为氢氧基或碳酸盐衍生物。然后,rac-[Cu(bpp)(H2O)]²⁺通过L-(+)-酒石酸作为手性洗脱剂,在SP Sephadex C-25上进一步分离成对映体[Cu(S,S-bpp)(H2O)]²⁺和[Cu(R,R-bpp)(H2O)]²⁺。三种立体异构体,meso-bpp、(S,S)-bpp和(R,R)-bpp,通过配体置换法,使用反式-1,2-二氨基环己烷-N,N,N′,N′-四乙酸(H₄cdta)从相应的铜(II)复合物中释放。使用高氯酸盐盐[meso-bppH2][ClO4]₂·2H₂O对meso异构体的结构进行了单晶X射线分析。