Parfenova Lyudmila V, Zakirova Irina V, Kovyazin Pavel V, Karchevsky Stanislav G, Istomina Galina P, Khalilov Leonard M, Dzhemilev Usein M
Institute of Petrochemistry and Catalysis, Russian Academy of Sciences, Prospect Oktyabrya, 141, 450075 Ufa, Russian Federation.
Institute of Petroleum Refining and Petrochemistry of the Republic of Bashkortostan, Iniciativnaya st., 12, 450065 Ufa, Russian Federation.
Dalton Trans. 2016 Aug 9;45(32):12814-26. doi: 10.1039/c6dt01366j.
The effect of solvent nature (CD2Cl2, d8-toluene, d8-THF) on the conformational behavior of neomenthyl-substituted zirconocenes CpIndZrCl2 (Cp = η(5)-C5H5, Ind = η(5)-neomenthylindenyl), CpCp'ZrCl2 (Cp = η(5)-C5H5, Cp' = η(5)-neomenthyl-4,5,6,7-tetrahydroindenyl), and Ind2ZrCl2 (Ind = η(5)-neomenthylindenyl) was shown by means of dynamic NMR spectroscopy, and the constants and thermodynamic parameters of conformer exchange were determined. The experimental conformational composition of the complexes was compared with structures obtained by quantum chemical modeling using the DFT methods PBE/3ζ and M06-2X/cc-pVDZ(H, C, Cl)/cc-pVDZ-PP(Zr), which predicted three rotamers in the case of both CpIndZrCl2 and CpCp'ZrCl2, and seven rotational isomers for Ind2ZrCl2, three of these being C2-symmetric and the others being asymmetric. The enantioselectivity of the conformationally mobile complex Ind2ZrCl2 in the reactions of terminal alkenes with AlR3 (R = Me, Et) was compared with that of rigid ansa-complexes, rac-p-S, p-S-[Y(η(5)-C9H10)2]ZrX2 (Y = SiMe2, C2H4; X = S-binaphtholate). Faster exchange between the conformers of Ind2ZrCl2 in a chlorinated solvent gives the structural isomer of catalytically active sites, which affords higher substrate conversion and reaction enantioselectivity. Binding of the ligands to ansa-zirconocenes prevents the rotational isomerism of the complexes, providing the same configuration of the β-stereogenic center in the methyl- and ethylalumination products (unlike the conformationally mobile complex Ind*2ZrCl2) with an enantiomeric purity of 50-65%.
通过动态核磁共振光谱研究了溶剂性质（CD2Cl2、d8 - 甲苯、d8 - 四氢呋喃）对新薄荷基取代的二氯锆茂CpIndZrCl2（Cp = η(5)-C5H5，Ind = η(5)-新薄荷基茚基）、CpCp'ZrCl2（Cp = η(5)-C5H5，Cp' = η(5)-新薄荷基 - 4,5,6,7 - 四氢茚基）和Ind2ZrCl2（Ind = η(5)-新薄荷基茚基）构象行为的影响，并确定了构象异构体交换的常数和热力学参数。将配合物的实验构象组成与使用DFT方法PBE/3ζ和M06 - 2X/cc - pVDZ(H, C, Cl)/cc - pVDZ - PP(Zr)通过量子化学建模获得的结构进行了比较，结果预测CpIndZrCl2和CpCp'ZrCl2均有三种旋转异构体，而Ind2ZrCl2有七种旋转异构体，其中三种是C2对称的，其他是不对称的。将构象可移动的配合物Ind2ZrCl2在末端烯烃与AlR3（R = Me，Et）反应中的对映选择性与刚性桥连配合物rac - p - S，p - S - [Y(η(5)-C9H]ZrX2（Y = SiMe2，C2H4；X = S - 联萘酚盐）的对映选择性进行了比较。在氯化溶剂中，Ind2ZrCl2构象异构体之间更快的交换产生了催化活性位点的结构异构体，从而实现了更高的底物转化率和反应对映选择性。配体与桥连锆茂的结合阻止了配合物的旋转异构现象，使得甲基铝化和乙基铝化产物中β - 立体中心具有相同的构型（与构象可移动的配合物Ind*2ZrCl相反），对映体纯度为50 - 65%。
