Centro de Química Estrutural, Complexo I, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001 Lisboa, Portugal.
Dalton Trans. 2014 Mar 14;43(10):3966-77. doi: 10.1039/c3dt52774c. Epub 2014 Jan 22.
A series of six new mixed-ligand dinuclear Mn(II,II) complexes of three different hydrazone Schiff bases (H3L(1), H3L(2) and H3L(3)), derived from condensation of the aromatic acid hydrazides benzohydrazide, 2-aminobenzohydrazide or 2-hydroxybenzohydrazide, with 2,3-dihydroxy benzaldehyde, respectively, is reported. Reactions of Mn(NO3)2·4H2O with the H3L(1-3) compounds, in the presence of pyridine (1 : 1 : 1 mole ratio), in methanol at room temperature, yield [Mn(H2L(1))(py)(H2O)]2(NO3)2·2H2O (1·2H2O), [Mn(H2L(2))(py)(CH3OH)]2(NO3)2·4H2O (2·4H2O) and [Mn(H2L(3))(py)(H2O)]2(NO3)2 (3) respectively, whereas the use of excess pyridine yields complexes with two axially coordinated pyridine molecules at each Mn(II) centre, viz. [Mn(H2L(1))(py)2]2(NO3)2·H2O (4·H2O), [Mn(H2L(2))(py)2]2(NO3)2·2H2O (5·2H2O) and [Mn(H2L(3))(py)2]2(NO3)2·2CH3OH (6·2CH3OH), respectively. In all the complexes, the (H2L(1-3))(-) ligand coordinates in the keto form. Complexes 1·2H2O, 2·4H2O, 4·H2O, 5·2H2O and 6·2CH3OH are characterized by single crystal X-ray diffraction analysis. The complexes 1, 2 and 6, having different coordination environments, have been selected for variable temperature magnetic susceptibility measurements to examine the nature of magnetic interaction between magnetically coupled Mn(II) centres and also for exploration of the catalytic activity towards microwave assisted oxidation of alcohols. A yield of 81% (acetophenone) is obtained using a maximum of 0.4% molar ratio of catalyst relative to the substrate in the presence of TEMPO and in aqueous basic solution, under mild conditions.
报告了一系列六个新的混合配体双核 Mn(II,II)配合物，这些配合物由三种不同的腙席夫碱（H3L(1)、H3L(2)和 H3L(3)）衍生而来，这些腙席夫碱是由芳香酸酰肼苯甲酰肼、2-氨基苯甲酰肼或 2-羟基苯甲酰肼与 2,3-二羟基苯甲醛缩合而成。在甲醇中，室温下，Mn(NO3)2·4H2O 与 H3L(1-3)化合物反应，在吡啶（1:1:1 摩尔比）存在下，生成[Mn(H2L(1))(py)(H2O)]2(NO3)2·2H2O（1·2H2O）、[Mn(H2L(2))(py)(CH3OH)]2(NO3)2·4H2O（2·4H2O）和[Mn(H2L(3))(py)(H2O)]2(NO3)2（3）。然而，使用过量的吡啶可以得到每个 Mn(II)中心轴向配位两个吡啶分子的配合物，即[Mn(H2L(1))(py)2]2(NO3)2·H2O（4·H2O）、[Mn(H2L(2))(py)2]2(NO3)2·2H2O（5·2H2O）和[Mn(H2L(3))(py)2]2(NO3)2·2CH3OH（6·2CH3OH）。在所有配合物中，(H2L(1-3))(-)配体以酮式配位。配合物 1·2H2O、2·4H2O、4·H2O、5·2H2O 和 6·2CH3OH 通过单晶 X 射线衍射分析进行了表征。选择具有不同配位环境的配合物 1、2 和 6 进行变温磁化率测量，以研究磁耦合 Mn(II)中心之间的磁性相互作用的性质，并探索其对微波辅助醇氧化的催化活性。在 TEMPO 和碱性水溶液存在下，在温和条件下，使用相对于底物最大 0.4%摩尔比的催化剂，可获得 81%（苯乙酮）的产率。
