The dinuclear complex 1 with cooperative hydrogen bonds can be prepared by the metal-directed reaction of Eq. (2). This work shows that the coordinated hydroxyl group trans to the secondary amino group is deprotonated more readily than that trans to the tertiary amino group and acts as the hydrogen-bond accepter. The lattice water molecules in 1 act as bridges between the two mononuclear units through hydrogen bonds. The complex is quite stable as the dimeric form even in various polar solvents. The complex exhibits a weak antiferromagnetic interaction between the metal ions in spite of relatively long Cu$\cdots$Cu distance. This strongly supports the suggestion that the antiferromagnetic behavior is closely related to the cooperative hydrogen bonds.
One of the current trends in molecular material science concerns the preparation and the study of materials combining several physical properties in a synergistic way. Organic/inorganic hybrids, in which organicor organometallicmoieties having a special physicochemical property are incorporated into a transition-metal cluster, may exhibit certain coupling phenomena between the d-electrons of inorganic transition-metal networks and the mobile πelectrons of the organic conjugated networks. Such coupling effects should provide us with rich opportunities to design and study molecular systems exhibiting special material characteristics, such as superconductivity, magnetism, electrical conductivity, optical properties, electrochromism, and catalytic activity. On the other hand, there is a considerable interest in the chemistry of multi-metallocenyl assemblies, particularly multi-ferrocenyl assemblies. Such compounds can be viewed as excellent candidates for multielectron reservoir systems, electron-transfer mediators, redox active materials for the modification of electrodes, ion sensors and/or materials for electronic devices. In this respect, if one hybridizes the multi-ferrocenyl moieties onto a transitionmetal cluster, the electrical and magnetic properties of both components will be probably combined in a synergistic way, leading to new properties applicable to the material science. However, the chemistry of the transition-metal clusters into which organic and/or organometallic moieties are incorporated, would be difficult to achieve a true advance mainly due to the poorly settled synthetic methods for such molecular assemblies. It is nearly impossible to prepare inorganic clusters having special functionalities in a bondby-bond fashion. One of the most plausible strategies for constructing such systems with their unique architecture will involve one-pot spontaneous self-assembly of components with required functionalities already in place. Such a strategy has been popularly utilized in organic chemistry and supramolecular inorganic chemistry. As an example of the related synthetic efforts, [Ni6(μ3Se)2(μ4-Se)3(dppf)3]Br2·3/2CHCl3 (1) was obtained by the self-assembly reaction of Ni(dppf)Br2 with Li2Se in the presence of Li[PhNC(O)Me] in THF. The first example of the [Ni6(μ3-Se)2(μ4-Se)3] cluster was prepared by the reaction of (NBu3)[NiCl3(PPh3)] with Se(SiMe3)2 and the similar reaction of [NiCl2(PPh3)2] with Se(SiMe3)2 produced [Ni12Se11Cl][NiCl3(PPh3)]2. 13 The structure of the cluster 1 is shown in Figure 1. The production of 1 from the present reaction is ascribed to the directional-bonding influence of the dppf ligand. During the course of the reaction, the fixed distance between the two phosphine atom of the ferrocene bridge may force the selective construction of the present prismatic structure. The existence of Li[PhNC(O)Me] was essential for an effective reaction. Without this anion it takes more than 14 days for the production of 1 to be detected by TLC. It is known that the addition of the [PhNC(O)Me]− ion suppresses the formation of an intractable polymer by complexing to the metal center and the more reactive anion temporarily displaces the less reactive bromide of the nickel before the attack of selenide, leading to the easy production of the cluster. 1 is soluble in THF and CHCl3, moderately soluble in hexane and sparingly soluble in polar solvents. It appears to be stable on exposure to moisture and air. X-ray
The reaction of stoichiometric amount of $FeCl_2{\cdot}4H_2O$, (2-pyridylmethyl, 3-pyridylmethyl)amine (2,3-pyma) and sodium azide/sodium thiocyanate in methanol under aerobic conditions affords the dinuclear Fe(III) complexes, [(2,3-pyma) $(N_3)_2Fe({\mu}-OCH_3)_2Fe(N_3)_2$(2,3-pyma)]${\cdot}CH_3OH$ (1) and [(2,3-pyma)$(NCS)_2Fe({\mu}-OCH_3)_2Fe(NCS)_2$(2,3-pyma)] (2) in good yield. Two bis-methoxy-bridged diiron(III) complexes are isolated and characterized. The coordination geometries around iron(III) ions in 1 and 2 are the same tetragonally distorted octahedron. The iron(III) ions are coordinated by two nitrogens of a 2,3-pyma, two nitrogens of two azide/thiocyanate ions, and two oxygens of two methoxy groups. Both compounds are isomorphous. The structures of 1 and 2 display the C-$H{\cdots}\pi$ and/or $\pi-\pi$ stacking interactions as well as hydrogen bonding interactions, respectively. Compounds 1 and 2 show significant antiferromagnetic couplings through the bridged methoxy groups between the iron(III) ions in the temperature range from 5 to 300 K ($H=-2JS_1{\cdot}S_2$, J=-19.1 and $-13.9\;cm^{-1}$ for 1 and 2).
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