Department of Material Science, Graduate School of Science, Osaka City University, Sumiyoshi-ku, Osaka 558-8585, Japan.
Dalton Trans. 2010 Jan 7(1):139-48. doi: 10.1039/b909491a. Epub 2009 Nov 9.
Dimanganese(III) complexes of salen-type ligands anchored by 9,9-dimethylxanthene-4,5-diyl spacers were synthesized. Two types of structures, cyclic and acyclic forms, are presented. The 2 + 2 Schiff-base condensation of 5,5'-(9,9-dimethylxanthene-4,5-diyl)bis(salicylaldehyde) and 1,2-diaminobenzene gave a macrocyclic ligand, from which a cyclic dimanganese(III) complex was synthesized. A similar dimanganese(III) complex with stereogenic centers was synthesized by the metal-assisted condensation reaction using (1R,2R)-1,2-diaminocyclohexane. Acyclic dimanganese(III) complexes anchored by one xanthene spacer were obtained by metal-assisted stepwise condensation reactions using the xanthene-bridged bis(salicylaldehyde), (1R,2R)-1,2-diaminocyclohexane monohydrochloride, and salicylaldehydes. X-Ray crystal structure analysis confirmed that both cyclic and acyclic complexes have two cofacially oriented salen-type manganese(III) units in a complex cation, showing an Mn...Mn distance of ca. 5.1 A. Asymmetric oxidation of sulfides was performed by using the chiral dimeric complexes as catalysts, which showed enantiomeric excesses ranging from 5 to 19%. The addition of 4-(dimethylamino)pyridine to the reaction system improved the enantioselectivity up to 39% ee. This effect was not observed for the corresponding mononuclear catalyst.
合成了由 9,9-二甲基芴-4,5-二基间隔基锚定的 salen 型配体的二锰(III)配合物。呈现出两种结构，即环状和无环形式。5,5'-(9,9-二甲基芴-4,5-二基)双(水杨醛)和 1,2-二氨基苯的 2 + 2 Schif f 碱缩合得到一个大环配体，由此合成了一个环状二锰(III)配合物。使用 (1R,2R)-1,2-二氨基环己烷通过金属辅助缩合反应合成了具有手性中心的类似二锰(III)配合物。通过使用芴桥联的双(水杨醛)、(1R,2R)-1,2-二氨基环己烷单盐酸盐和水杨醛的金属辅助逐步缩合反应，获得了由一个芴间隔基锚定的无环二锰(III)配合物。X 射线晶体结构分析证实，环状和无环配合物在一个配合物阳离子中都具有两个共面取向的 salen 型锰(III)单元，显示出约 5.1 A 的 Mn...Mn 距离。使用手性二聚体配合物作为催化剂进行了硫化物的不对称氧化，其对映体过量范围为 5 至 19%。向反应体系中添加 4-(二甲氨基)吡啶可将对映选择性提高至 39%ee。对于相应的单核催化剂，没有观察到这种效果。
