Centro de Química Estrutural, Complexo I, Instituto Superior Técnico, University of Lisbon, Av. Rovisco Pais, 1049-001 Lisboa, Portugal.
Dalton Trans. 2013 Dec 21;42(47):16578-87. doi: 10.1039/c3dt52453a.
Three new tetranuclear copper(II) complexes [Cu(HL(1))]4·4EtOH (1·4EtOH), [Cu(HL(2))]4 (2) and [Cu(H2L(3))]4(NO3)4·2H2O (3·2H2O) have been synthesized using three different hydrazone Schiff base ligands derived from the condensation of the aromatic acid hydrazides 2-hydroxybenzo-, 2-aminobenzo- or benzo-hydrazide, with 2,3-dihydroxybenzaldehyde. Complexes 1 and 3 have been characterized by single crystal X-ray diffraction analysis. The coordinating behaviour of the ligand depends on the nature of the ortho substituent present in the hydrazide moiety. The ligands bearing a strong electron donating group (by resonance) in the ortho position undergo complexation via enolization and deprotonation, whereas the absence of such an effect leads to complexation via the keto form, and two different types of tetranuclear Cu(II) clusters, viz. open-cubane and cubane, are obtained. Variable temperature magnetic susceptibility measurements of complexes 1 and 3 have been carried out to examine the nature of magnetic interaction between the Cu(II) centres. All the three complexes (1-3) act as good catalyst precursors towards mild hydrocarboxylation of linear and cyclic alkanes into carboxylic acids in water-acetonitrile medium.
三种新型四核铜(II)配合物[Cu(HL(1))]4·4EtOH(1·4EtOH)、[Cu(HL(2))]4(2)和[Cu(H2L(3))]4(NO3)4·2H2O(3·2H2O)已通过三种不同的腙希夫碱配体的缩合合成，这些配体来自芳族酸酰肼 2-羟基苯甲酰肼、2-氨基苯甲酰肼或苯甲酰肼与 2,3-二羟基苯甲醛的缩合。配合物 1 和 3 已通过单晶 X 射线衍射分析进行了表征。配体的配位行为取决于酰肼部分中邻位取代基的性质。带有强供电子基团（通过共振）的配体通过烯醇化和去质子化进行配位，而不存在这种效应则导致通过酮式进行配位，并获得两种不同类型的四核 Cu(II)簇，即开笼型和笼型。对配合物 1 和 3 的变温磁化率测量已进行，以研究 Cu(II)中心之间的磁相互作用的性质。所有三种配合物(1-3)在水-乙腈介质中均能作为良好的催化剂前体，将线性和环状烷烃温和地转化为羧酸。
