Stereocontrol in Dinuclear Triple Lithium-Bridged Titanium(IV) Complexes: Solving Some Stereochemical Mysteries
作者:Markus Albrecht、Elisabeth Isaak、Verena Moha、Gerhard Raabe、Roland Fröhlich
DOI:10.1002/chem.201402370
日期:2014.5.26
strongly depends on the donor ability of the solvent. Usually, in solvents with high donor ability, the stereochemically labile monomer is preferred, whereas in nondonor solvents, the dimer is the major species. In the latter, the stereochemistry at the complex units is “locked”. The configuration at the titanium(IV) triscatecholates is influenced by addition of chiral ammonium countercations. In this
化合物1 a – f ‐ H 2形成“单体”三儿茶酚钛(IV)配合物[Ti(1 a – f)3 ] 2−,在存在锂离子的情况下与三价锂桥联的“二聚体”处于平衡状态[Li 3(Ti(1 a – f)3)2 ] -。平衡在很大程度上取决于溶剂的供体能力。通常,在具有高供体能力的溶剂中,优选立体化学不稳定的单体,而在非供体溶剂中,二聚体是主要物质。在后者中,复杂单元的立体化学是“锁定的”。三儿茶酚钛(IV)的构型受手性铵抗衡阳离子添加的影响。在这种情况下,在单体处诱导的立体化学信息被转移至二聚体。或者,可以通过对映体纯的酯侧链控制金属配合物的构型。由于单体或二聚体中酯基的取向不同,对于[Ti(1 c– e)3 ] 2-或[Li 3(Ti(1 c - e)3)2 ] -。对于二聚体[Li 3(Ti(1f)3)2 ] -发现了一个令人惊讶的例外。在此,二聚体是弱供体(甲醇)和强供体(DMSO)溶剂中