The speciation of homochiral and heterochiral diastereomers of homoleptic cobalt(II) and zinc(II) PyBox complexes
The speciation of homochiral and heterochiral diastereomers of homoleptic cobalt(II) and zinc(II) PyBox complexes
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DOI：
10.1016/j.poly.2018.04.030
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发表时间：
2018-07
期刊：
影响因子：
2.6
通讯作者：
Kay E Burrows;Rafal Kulmaczewski;O. Cespedes;S. Barrett;M. Halcrow
中科院分区：
文献类型：
--
作者：
Kay E Burrows;Rafal Kulmaczewski;O. Cespedes;S. Barrett;M. Halcrow
制备并表征了[Zn（LPh）2][BF 4]2、[Zn（LiPr）2][BF 4]2、[Co（LPh）2][BF 4]2和[Co（LiPr）2][BF 4]2的同手性[M（（R）-LR）2]2+和异手性[M（（R）-LR）（（S）-LR）]2+异构体（LPh= 2，6-双（4-苯基恶唑啉基）吡啶;LiPr= 2，6-双（4-异丙基恶唑啉基）吡啶）。其中6个化合物的晶体学特征表明，配体取代基之间的空间排斥导致更扭曲的协调几何结构中的同手性异构体，特别是在theLiPr配合物。异手性[M（（R）-LiPr）（（S）-LiPr）]2+（M = Zn或Co）在CD 3CN中通过配体再分配反应发生部分外消旋化，而[M（（R）-LPh）（（S）-LPh）]2+则不发生外消旋化（与以前的报道一致）。这可能是[M（（R）-LPh）（（S）-LPh）]2+中分子内π... π-相互作用的结果，其中每个吡啶基被夹在来自另一个LPh配体的两个苯基取代基之间。这些π... π-相互作用在纯手性[M（（R）-LR）2]2+中被破坏，这是由于该异构体中苯基取代基之间的上述空间冲突。
Homochiral [M((R)-LR)2]2+and heterochiral [M((R)-LR)((S)-LR)]2+isomers of [Zn(LPh)2][BF4]2, [Zn(LiPr)2][BF4]2, [Co(LPh)2][BF4]2, and [Co(LiPr)2][BF4]2(LPh= 2,6-bis(4-phenyloxazolinyl)pyridine;LiPr= 2,6-bis(4-isopropyloxazolinyl)pyridine) have been prepared and characterised. Six of the eight compounds were crystallographically characterised, showing that steric repulsions between ligand substituents lead to more distorted coordination geometries in the homochiral isomers, especially in theLiPrcomplexes. Heterochiral [M((R)-LiPr)((S)-LiPr)]2+(M = Zn or Co) undergoes partial racemisation in CD3CN through ligand redistribution reactions, whereas [M((R)-LPh)((S)-LPh)]2+does not (in agreement with previous reports). This may be a consequence of intramolecularπ…π-interactions in [M((R)-LPh)((S)-LPh)]2+, whereby each pyridyl group is sandwiched between two phenyl substituents from the otherLPhligand. Theseπ…π-interactions are disrupted in homochiral [M((R)-LR)2]2+, owing to the aforementioned steric clash between phenyl substituents in that isomer.