First Observation of Zn−CN Bond in “Highly Coordinated” Mixed Organozincates by EXAFS Spectroscopy
First Observation of Zn−CN Bond in “Highly Coordinated” Mixed Organozincates by EXAFS Spectroscopy
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通过 EXAFS 光谱首次观察到“高度配位”混合有机锌酸盐中的 Zn−CN 键
DOI：
10.1021/ja971502o
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发表时间：
1997
影响因子：
15
通讯作者：
T. Sakamoto*
中科院分区：
文献类型：
--
作者：
M. Uchiyama;Y. Kondo;T. Miura;T. Sakamoto*
三有机锌盐，符号为R3ZnM(M)Li，Na等)，是一种用途广泛的试剂，不仅用于构建碳碳键1，而且还用于芳香卤化物或卤乙烯化合物的金属化。3作为一种新型的锌酸盐，我们报道了“高度配位的”锌酸盐，Me3Zn(R)Li2(R)Me，CN，SCN)可用于芳基卤化物的金属化和各种有机部分的选择性转移到羰基化合物(图1)。4基于优良的化学产率和化学选择性，这些物种被认为与普通的三有机锌酸盐R3ZnLi有所区别。然而，活性物种的反应机理和真实结构是一个有争议的话题。另一方面，从1981年开始，利普舒茨等人。发表了一系列关于“高阶”混合铜酸盐R_2Cu(CN)Li_2的论文，暗示在铜、5上含有三个共价键配体的双阴离子铜(I)物种，这些铜酸盐的结构一直是一个有争议的问题。6然而，最近的结构研究表明，R2Cu(CN)Li2不是“高阶”铜酸盐，也不是双阴离子铜(I)盐，而是改性的Gilman型铜酸盐。7我们现在通过EXAFS、~1H核磁共振和拉曼光谱研究，描述了支持锌酸盐存在的主要证据，即四配位的双阴离子锌(II)物种。扩展X射线吸收精细结构(EXAFS)谱探测原子或离子周围的局域结构，即原子或离子周围的近邻的性质、数目和距离
Triorganozincates, symbolized as R3ZnM (M) Li, Na, etc.), are versatile reagents not only for the construction of carboncarbon bonds1 but also for the metalation of aromatic halides2 or vinyl halides. 3 As a new type of zincates, we reported that “highly coordinated” zincates, Me3Zn (R) Li2 (R) Me, CN, SCN) are synthetically useful for the metalation of aryl halides and for the selective transference of various organic moieties to carbonyl compounds (Figure 1). 4 On the basis of the excellent chemical yields and the chemoselectivity, these species were considered to be differentiated from ordinary triorganozincates, R3ZnLi. However, the reaction mechanism and the real structure of active species are a topic of controversial discussions.On the other hand, beginning in 1981, Lipshutz et al. published a series of papers about “higher order” mixed cuprates, R2Cu (CN) Li2, implying dianionic Cu (I) species containing three covalently bonded ligands on Cu, 5 and the structure of these cuprates has been a controversial issue. 6 However, recent studies on the structure revealed that R2Cu (CN) Li2 are not “higher order” cuprates, dianionic Cu (I) salts, but modified Gilman-type cuprates. 7 We now describe primary evidence supporting the existence of “highly coordinated” zincates, namely, tetracoordinated dianionic Zn (II) species, by use of EXAFS, 1H NMR, and Raman spectroscopic studies. Extended X-ray absorption fine structure (EXAFS) spectroscopy probes the local structures, ie, the nature, number, and distance of near neighbors which surround atoms or ions, of a