Roymuhury Sagnik K, Chakraborty Debashis, Ramkumar Venkatachalam
Department of Chemistry, Indian Institute of Technology Patna, Patna 800 013, Bihar, India.
Dalton Trans. 2015 Jun 14;44(22):10352-67. doi: 10.1039/c5dt01092f.
A series of Ti(iv), Zr(iv) and Hf(iv) complexes containing imine based bis-bidentate ligands were synthesized and characterized by various spectroscopic techniques, elemental analysis and X-ray crystallography. The ligands m-xysal-((t)Bu)4 (L(1)((t)Bu)4), m-xysal-(Me)2((t)Bu)2 (L(2)Me2((t)Bu)2) and m-xysal-(Cl)4 (L(3)Cl4) were reacted with Ti(O(i)Pr)4, Zr(O(i)Pr)4·(i)PrOH and Hf(O(t)Bu)4 in a 1 : 1 stoichiometric ratio to form complexes (L2M2(OR)4, where L = m-xysal-((t)Bu)4, m-xysal-(Me)2((t)Bu)2 and m-xysal-(Cl)4, M = Ti and R = (i)Pr, (L2M2(OR)4, where L = m-xysal-((t)Bu)4, m-xysal-(Me)2((t)Bu)2 and m-xysal-(Cl)4, M = Zr and R = (i)Pr and (L3M3(OR)6, where L = m-xysal-((t)Bu)4, m-xysal-(Me)2((t)Bu)2 and m-xysal-(Cl)4, M = Hf and R = (t)Bu respectively. Complex was crystallized from a 1 : 1 : 1 mixture of chloroform, ethanol and toluene to yield an ethoxy substituted complex (L2M2(OR)4, L = m-xysal-(Me)2((t)Bu)2, M = Zr and R = Et. The X-ray structures of , and illustrate that and are binuclear helical complexes, whereas is trinuclear. These complexes were found to be active for the ring opening polymerization (ROP) of lactides (rac-LA, l-LA) and epoxides. All the complexes produced atactic poly(lactic acid) (PLA) with good number average molecular weight (Mn) and narrow molecular weight distributions (MWDs). The magnetic isotropic shielding constants were calculated using the GIAO/B3LYP/LANL2DZ approach and correlated with the experimental values. The HOMO-LUMO energy band gaps and Mulliken charges were calculated using the DFT method to explain the reactivity of these complexes according to the relationship between chemical hardness and reactivity established by Pearson. In addition, complexes , activated by methylaluminoxane (MAO), were used and found to be moderately active for ethylene polymerization.
合成了一系列含有基于亚胺的双齿配体的钛（IV）、锆（IV）和铪（IV）配合物，并通过各种光谱技术、元素分析和X射线晶体学对其进行了表征。配体间二甲苯水杨醛-（叔丁基）4（L(1)(叔丁基)4）、间二甲苯水杨醛-（甲基）2（叔丁基）2（L(2)Me2(叔丁基)2）和间二甲苯水杨醛-（氯）4（L(3)Cl4）与四异丙醇钛、四异丙醇锆·异丙醇和四叔丁醇铪按1:1化学计量比反应，形成配合物（L2M2(OR)4，其中L = 间二甲苯水杨醛-（叔丁基）4、间二甲苯水杨醛-（甲基）2（叔丁基）2和间二甲苯水杨醛-（氯）4，M = Ti且R = 异丙基）、（L2M2(OR)4，其中L = 间二甲苯水杨醛-（叔丁基）4、间二甲苯水杨醛-（甲基）2（叔丁基）2和间二甲苯水杨醛-（氯）4，M = Zr且R = 异丙基）以及（L3M3(OR)6，其中L = 间二甲苯水杨醛-（叔丁基）4、间二甲苯水杨醛-（甲基）2（叔丁基）2和间二甲苯水杨醛-（氯）4，M = Hf且R = 叔丁基）。配合物从氯仿、乙醇和甲苯的1:1:1混合物中结晶，得到乙氧基取代的配合物（L2M2(OR)4，L = 间二甲苯水杨醛-（甲基）2（叔丁基）2，M = Zr且R = 乙基）。[具体配合物名称1]、[具体配合物名称2]和[具体配合物名称3]的X射线结构表明，[具体配合物名称1]和[具体配合物名称2]是双核螺旋配合物，而[具体配合物名称3]是三核的。发现这些配合物对丙交酯（外消旋丙交酯、左旋丙交酯）和环氧化物的开环聚合（ROP）具有活性。所有配合物均产生具有良好数均分子量（Mn）和窄分子量分布（MWD）的无规聚乳酸（PLA）。使用GIAO/B3LYP/LANL2DZ方法计算磁各向同性屏蔽常数，并与实验值相关联。使用DFT方法计算HOMO-LUMO能带隙和Mulliken电荷，以根据Pearson建立的化学硬度与反应性之间的关系解释这些配合物的反应性。此外，使用经甲基铝氧烷（MAO）活化的配合物[具体配合物名称4]，发现其对乙烯聚合具有中等活性。
