SYNTHESIS AND STRUCTURAL AND MAGNETIC CHARACTERIZATION OF THE ALKOXO-BRIDGED CHROMIUM(III) DIMER DI-μ-METHOXO-BIS(BIS(3-CHLORO-2,4-PENTANEDIONATO)CHROMIUM(III))
SYNTHESIS AND STRUCTURAL AND MAGNETIC CHARACTERIZATION OF THE ALKOXO-BRIDGED CHROMIUM(III) DIMER DI-μ-METHOXO-BIS(BIS(3-CHLORO-2,4-PENTANEDIONATO)CHROMIUM(III))
复制标题
烷氧桥联铬(III)二聚体DI-μ-甲氧基-双(双(3-氯-2,4-戊二酮)铬(III))的合成及其结构和磁学表征
作者：
E. D. Estes;R. Scaringe;W. Hatfield;D. Hodgson
简介 铜 (II) 和铬 (III) 的羟基桥和烷氧基桥二聚体中的磁相互作用的研究最近受到了广泛的关注。 1, 2 已经证明3" 6 对于最简单的情况，即铜 (II) 的二氢桥联二聚体，交换积分 J 的大小和符号主要由 Cu-O-Cu 桥接角的值决定，尽管其他作者 7, 8 指出金属中心平面几何形状的扭曲也会影响 J 的大小。对于类似的铬 (III) 配合物，磁交换由于存在多个而变得非常复杂每个金属中心都有不成对的电子，这导致除了 a 系统之外，二聚体系统中也存在不成对的自旋。 然而，有一个简化的特征，即 [CrL20H] 2n+ 和 [CrL20R] 2M+ 类型的所有配合物（其中 L 是二齿配体）中铬的几何形状是伪八面体，因此，在整个系列中，铬的几何形状大致恒定。因此，我们已经开始研究这些类型的铬 (III) 二聚体的结构和磁性，并在其他地方报告了我们对几种羟基桥接物种的研究结果2, 9" 12。我们在这里报告了第一个完全表征的二烷氧基桥联铬二聚体的合成、结构和磁性，该络合物是二-#t-甲氧基-双[双(3-氯-2, 4-戊二酮)铬(III)]。
Introduction The study of the magnetic interactions in hydroxo-and alkoxo-bridged dimers of copper (II) and chromium (III) has received extensive recent attention. 1, 2 It has been demonstrated3" 6 for the simplest case, ie the dihydroxobridged dimers of copper (II), that the magnitude and sign of the exchange integral J are principally determined by thevalue of the Cu-O-Cu bridging angle, although other authors7, 8 have noted that distortions from planar geometry atthe metal center also influence the magnitude of J. For the analogous chromium (III) complexes the magnetic exchange is greatly complicated by the presence of more than one unpaired electron at each metal center, which leads to unpaired spin in the system of the dimer in addition to that in the a system. There is, however, one simplifying feature in that the geometry at chromium in all complexes of the types [CrL20H] 2n+ and [CrL20R] 2M+(where L is a bidentate ligand) is pseudooctahedral and, therefore, approximately constant throughout the series. Hence, the probable influence7 of changes in the geometry at the metal on the magnetic exchange does notintrude here. We have, therefore, initiated studies on the structural and magnetic properties of chromium (III) dimers of these types and have reported elsewhere2, 9" 12 the results of our studies of several hydroxo-bridged species. We here report the synthesis, structure, and magnetic properties of the first completely characterized dialkoxo-bridged dimer of chromium, the complex being di-# t-methoxo-bis [bis (3-chloro-2, 4-pentanedionato) chromium (III)].