X-ray determination of the absolute configuration of metal complexes in quasiracemic crystals. .LAMBDA.-(-)546-Cobalt(III) acetylacetonate
X-ray determination of the absolute configuration of metal complexes in quasiracemic crystals. .LAMBDA.-(-)546-Cobalt(III) acetylacetonate
复制标题
X 射线测定准外消旋晶体中金属配合物的绝对构型。
DOI：
10.1021/ja00748a062
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发表时间：
1971
期刊：
影响因子：
--
通讯作者：
R. Dreele
中科院分区：
文献类型：
--
作者：
R. C. Fay;R. Dreele
4937，其绝对构型已由单晶X射线方法确定为A-（+）589-iro/z-tris-[（+）-3-acetylacetylacetorato] chromium（III）。图5部分溶解的Co（acac）86的混合物的结晶（[] 54 π =-20，200）和外消旋Al（acac）3（~ 1：10 v/v）得到了含有过量（-）S_（46）-Co（acac）_3的准外消旋单斜晶体，其晶格参数为（a= 13.96±0.02，B=7.53±0.01，c= 16.32±0.02 A，ε =98.66±0.05）与外消旋Co（acac）3和外消旋Al（acac）3的同晶晶体几乎相同。在准外消旋Co（acac）3-Al（acac）3混晶中，Co在两个对映体位置的不相等取代足以使空间群对称性从中心对称的P2 l/c降低到非中心对称的P2 i，而不需要改变原子坐标。对于本测定所用的晶体，在A0/上的反射l- 2n+ 1，通常对于P2 i/c是消失的，看起来很弱，但相当尖锐。从用Ni过滤的Cu Ka辐射拍摄的多次曝光旋进照片中视觉估计来自四个层A0 1、7、0 k1和1 k1的268次反射的强度数据。层内缩放的强度进行与洛伦兹偏振和斑点延伸被施加的校正。由于准外消旋晶体与Co（III）、7 Al（III）、7和Mn（III）的外消旋三乙酰丙酮化物是同晶型的，因此使用先前公布的这三种配合物的结构参数对占位因子和层间尺度因子（六个参数）进行了8次修正。这些修正的结果只采用了Co 0、Al 0、C和O 0的散射因子的真实的部分，9-10总结在表I中。很明显，
4937 whose absolute configuration has been establishedby single-crystal X-ray methods is A-(+) 589-iro/zs-tris-[(+)-3-acetylcamphorato] chromium (III). 5 Crystallization of a mixture of partially resolved Co (acac) 86 ([] 54ß=-20,200) and racemic Al (acac) 3 from benzene-hexane (~ 1: 10 v/v) gives quasiracemic monoclinic crystals which contain an excess of (—) s46-Co (acac) 3 andwhich display lattice parameters (a= 13.96±0.02, b=7.53±0.01, c= 16.32±0.02 A, ß=98.66±0.05) nearly identicalwith those for the isomorphous crystals of racemic Co (acac) 3 and racemic Al (acac) 3.7 However, the quasiracemic crystals show only the space group symmetry P2i instead of P21jc, that observed for the racemic acetylacetonates. In the quasiracemic Co (acac) 3-Al (acac) 3 mixed crystals, unequal substitutionof cobalt inthe two enantiomeric sites suffices to reduce the space group symmetry from the centrosymmetric P2l/c to the noncentrosymmetric P2i without requiring any change in atomic coordinates. For the crystal used in this determination, the reflec-tions l— 2n+ 1 on A0/, normally extinct for P2i/c, appeared weakly but were quite sharp. Intensity data on 268 reflections from the four layers A0/, 7, 0kl, and\kl were estimated visually from multiple-exposure precession photographs taken with Ni-filtered Cu Ka radiation. Intralayer scaling of the intensities was performed with corrections for Lorentzpolarization and spot extension being applied. Since the quasiracemiccrystal is isomorphous with the racemic trisacetylacetonates of Co (III), 7 Al (III), 7 and Mn (III), 8 refinements of the site occupancies and interlayer scale factors (six parameters) were carried out using the previously published structural parameters for these three complexes. The results of these refine-ments, which employedonly the real part of the scatter-ing factors for Co0, Al0, C, and O0, 9-10 are summarized in Table I. It is quite clear that there is no significance