Department of Chemistry and Biochemistry, The Ohio State University, 100 W. 18th Ave., Columbus, OH 43210, USA.
Dalton Trans. 2014 Feb 21;43(7):2781-8. doi: 10.1039/c3dt52553h.
The preparation, single crystal and molecular structures of the compounds (BDI)Mg(OCMe2COOEt)(L) are described where BDI = 2-[(2,6-diisopropylphenyl)amino]-4-[(2,6-diisopropylphenyl)imino]pent-2-ene and L = pyridine (py) and 4-dimethylaminopyridine (DMAP). In the solid-state the molecules have five coordinate Mg(2+) ions that may be considered as derived from a trigonal bipyramid where the chelating BDI and OCMe2COOEt ligands span equatorial-axial sites. IR spectroscopic data obtained in CH2Cl2 indicate that the chelating nature of the OCMe2COOEt ligand is maintained in solution and variable temperature NMR studies reveal that the ligands py or DMAP undergo a rapid reversible dissociation in toluene-d8 and especially in THF-d8. This leads to a facile exchange involving coordinated and free L upon the addition of L and evidence is presented to support the view that this occurs exclusively by a dissociative interchange mechanism. Zinc forms a related complex (BDI)Zn(OCMe2COOEt) lacking additional coordination of L but maintaining the chelating nature of the OCMe2COOEt ligand and undergoing reversible coordination of L in the presence of added ligands L. The magnesium and zinc complexes will initiate and sustain the living polymerization of lactide (L- or rac-LA) but not the ring-opening polymerization of ε-caprolactone.
化合物（BDI）Mg（OCMe2COOEt）（L）的制备、单晶和分子结构描述，其中BDI=2-[(2,6-二异丙基苯基)氨基]-4-[(2,6-二异丙基苯基)亚氨基]戊-2-烯，L=吡啶（py）和 4-二甲氨基吡啶（DMAP）。在固态中，分子具有五配位的 Mg(2+)离子，可被认为是衍生自三角双锥，其中螯合的 BDI 和 OCMe2COOEt 配体跨越赤道-轴向位置。在 CH2Cl2 中获得的红外光谱数据表明，OCMe2COOEt 配体的螯合性质在溶液中得以保持，而变温 NMR 研究表明，配体 py 或 DMAP 在甲苯-d8 中特别是在 THF-d8 中发生快速可逆解离。这导致了配位和游离 L 的易于交换，并且有证据表明这种交换仅通过解离交换机制发生。锌形成了一种相关的配合物（BDI）Zn（OCMe2COOEt），缺乏 L 的额外配位，但保持了 OCMe2COOEt 配体的螯合性质，并在添加的配体 L 存在下可逆配位 L。镁和锌配合物将引发并维持丙交酯（L-或 rac-LA）的活性聚合，但不能引发ε-己内酯的开环聚合。
