溴化顺式-溴•氨•二(乙二胺)合钴(III)绝对不对称合成与拆分机理*

分别用绝对不对称合成和改进的拆分方法制备标题配合物Λ-(+)D-cis-CoBr(NH3)(en)2]Br2(1)和Δ-(-)D-cis-CoBr(NH3)(en)2]Br2(2), 以及制备了cis-CoBr(NH3)(en)2]Br2·2H2O(3)(en=1,2-乙二胺). 用元素分析、差热-热重、旋光度、UV-Vis、CD 光谱等对产物进行了表征.通过CD 光谱法获得了绝对不对称合成Co(III)配合物的产物ee 值分布图援当利用绝对不对称合成得到的手性Co(III)配合物去“逆向拆分”外消旋溴代樟脑磺酸铵NH4(dl-BCS)]时只获得部分拆分, 初步认为这与交互拆分过程中阴阳离子之间的有效手性识别有关, 对于手性Co(III)配合物的绝对不对称合成还提出了一个新的反应机理,即“催化-结晶诱导”机理.

Absolute Asymmetric Synthesis and Resolution Mechanism of Chiral cis-bromoamminebis(ethylenediamine)cobalt(Ⅲ) Bromide

The absolute asymmetric synthesis of the title complexes Λ-(+)D-cis-CoBr(NH3)(en)2]Br2(1) and Δ-(-)D-cis-CoBr(NH3)(en)2]Br2(2)(en=1,2-ethylenediamine) as well as the improved optical resolution of cis-CoBr(NH3)(en)2]Br2·2H2O(3) are described in detail. The products were characterized by means of elemental analysis, TG-DTA, optical rotation, UV-Vis, and CD spectra. The distribution of enantiomeric excess(ee) of cis-CoBr(NH3)(en)2]Br2 in the absolute asymmetric synthesis was obtained by the measurements of their CD spectra. It was found that the complete resolution of rac-cis-CoBr(NH3)(en)2]Br2·2H2Owas achieved by use of NH4(d-BCS) (ammonium d-α-bromocamphor-π-sulfonate) or NH4(l-BCS) while NH4(dl-BCS) could only be partially resolved by chiral cis-CoBr(NH3)(en)2]Br2 at the same condition. It is deduced that there are notable differences in the chiral discrimination of the reciprocal resolution between cis-CoBr(NH3)(en)2]Br2 and NH4BCS.Moreover, a new“catalysis-crystal induction”mechanismin the preparation of the chiral Co(III) complex is put forward.