Lehrstuhl für Anorganische Chemie I, Fakultät für Chemie, Universität Bielefeld, D-33615 Bielefeld, Germany.
Inorg Chem. 2009 Oct 5;48(19):9476-84. doi: 10.1021/ic901325y.
The synthesis of a chiral version of a triplesalen ligand has been performed in two steps starting from 2,4,6-triacetyl-1,3,5-trihydroxybenzene (1). Reaction with excess trans-(1R,2R)-1,2-cyclohexanediamine and trans-(1S,2S)-1,2-cyclohexanediamine provided the chiral triplesalen half units 2,4,6-tris[1-((1R,2R)-2-aminocyclohexylimino)ethyl]-1,3,5-trihydroxybenzene (2(RR)) and 2,4,6-tris[1-((1S,2S)-2-aminocyclohexylimino)ethyl]-1,3,5-trihydroxybenzene (2(SS)), respectively. The two enantiomeric pure triplesalen ligands H(6)chand(RR) and H(6)chand(SS) were obtained by reaction of the triplesalen half units with 3,5-di-tert-butylsalicylaldehyde. Reaction with MnCl(2) x 2 H(2)O under basic aerobic conditions afforded the chiral trinuclear triplesalen complexes 3(RR) and 3(SS). Single-crystal X-ray diffraction studies on both enantiomers showed the presence of the two ionization isomers [(chand){Mn(III)Cl(MeOH)}(3)] and [(chand){Mn(III)(MeOH)(2)}(3)]Cl(3) in the solid state, resulting in the formulation of 3 (either 3(RR) or 3(SS)) as [(chand){Mn(III)Cl(MeOH)}(3)][(chand){Mn(III)(MeOH)(2)}(3)]Cl(3). The crystal structures exhibit chiral hydrophobic channels of approximately 8 A diameter decorated with tert-butyl groups. These form left-handed helices in the 3(RR) enantiomer and right-handed helices in the 3(SS) enantiomer. Magnetic measurements are in accord with weak exchange interactions between the Mn(III) S(i) = 2 ions and strong local magnetic anisotropy as has been found in other trinuclear Mn(III)(3) triplesalen complexes. As a proof-of principal, we have investigated the catalytic ability of the two enantiomers in the enantioselective epoxidation of unfunctionalized olefins. The chiral trinuclear Mn(III)(3) triplesalen acts under non-optimized conditions as a catalyst with relatively good yields and moderate enantiomeric excess.
已通过两步反应从 2,4,6-三乙酰-1,3,5-三羟基苯（1）合成了手性三联沙林配体。与过量的反式-（1R,2R）-1,2-环己二胺和反式-（1S,2S）-1,2-环己二胺反应，得到手性三联沙林半单位 2,4,6-三[1-（（1R,2R）-2-氨基环己基亚氨基）乙基]-1,3,5-三羟基苯（2（RR））和 2,4,6-三[1-（（1S,2S）-2-氨基环己基亚氨基）乙基]-1,3,5-三羟基苯（2（SS））。通过三联沙林半单位与 3,5-二叔丁基水杨醛反应，得到两种对映体纯三联沙林配体 H（6）chand（RR）和 H（6）chand（SS）。在碱性有氧条件下与 MnCl（2）x2H（2）O 反应，得到手性三核三联沙林配合物 3（RR）和 3（SS）。对两种对映异构体的单晶 X 射线衍射研究表明，在固态中存在两种离子化异构体[(chand){Mn（III）Cl（MeOH）}（3）]和[(chand){Mn（III）（MeOH）（2）}（3）]Cl（3），导致 3（无论是 3（RR）还是 3（SS））的化学式为[(chand){Mn（III）Cl（MeOH）}（3）][(chand){Mn（III）（MeOH）（2）}（3）]Cl（3）。晶体结构显示出约 8 A 直径的手性疏水性通道，这些通道用叔丁基修饰。在 3（RR）对映异构体中形成左手螺旋，在 3（SS）对映异构体中形成右手螺旋。磁性测量与其他三核 Mn（III）（3）三联沙林配合物中发现的 Mn（III）S（i）=2 离子之间的弱交换相互作用和强局部各向异性一致。作为原理的证明，我们研究了两种对映体在手性三核 Mn（III）（3）三联沙林催化下非官能化烯烃的对映选择性环氧化中的催化能力。在非优化条件下，手性三核 Mn（III）（3）三联沙林作为催化剂表现出相对较高的产率和中等的对映体过量。
