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Tetranuclear Cluster (tetranuclear + cluster)
Selected AbstractsA Zig-Zag [MnII4] Cluster from a Novel Bis(,-diketonate) LigandEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 10 2006Guillem Aromí Abstract A new ligand, H5L3, has been synthesized featuring seven linearly arranged oxygen donors in form of two 1,3-diketone and three phenol groups. The X-ray structure of H5L3 unveils a rare case where one of the diketones is in the enolic form and the other one in the bis(carbonyl) form. This structure is shown by 1H NMR to persist in solution. Reaction of H5L3 with Mn(AcO)2 in pyridine leads to the novel tetranuclear cluster [Mn4(H2L3)2(OAc)2(py)5] (1), which displays an unusual core in form of a zig-zag chain. Bulk magnetic measurements revealed the existence of weak antiferromagnetic coupling within the molecule. Numerical fits to a model described by the Hamiltonian H = ,2J1(S1S2 + S3S4) , 2J2(S2S3) yield coupling constants of J1 = ,2.23 cm,1, J2 = ,0.85 cm,1 and g = 2.08. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source] Dithiolate-Bridged Fe-Ni-Fe Trinuclear Complexes Consisting of Fe(CO)3,n(CN)n (n=0, 1) Components Relevant to the Active Site of [NiFe] HydrogenaseCHEMISTRY - AN ASIAN JOURNAL, Issue 6 2009Satyanarayan Pal Dr. Abstract Step-by-step: A trinuclear Fe-Ni-Fe complex 1 was synthesized from the reaction of [Fe(CO)4I2] with Li2[Ni(norbornane- exo -2,3-dithiolate)2]. The CO ligands in 1 were transformed into CN, upon treatment with ,N(SiMe3)2, and the monocyanide complex 3 and the dicyanide complex 4 were obtained. Complexes 3 and 4 were found to react with protonic acids, whereas 1 is robust. A dithiolate-bridged Fe-Ni-Fe trinuclear carbonyl complex [(CO)3Fe(,-ndt)Ni(,-ndt)Fe(CO)3] (1, ndt=norbornane- exo -2,3-dithiolate) has been synthesized from the reaction of [Fe(CO)4I2] and Li2[Ni(ndt)2]. This reaction was found to occur with concomitant formation of a tetranuclear cluster [Ni3(,-ndt)4FeI] (2). Treatment of 1 with Na[N(SiMe3)2] transforms some of the CO ligands into CN,, and the monocyanide complex (PPh4)[(CO)2(CN)Fe(,-ndt)Ni(,-ndt)Fe(CO)3] (3) and the dicyanide complex (PPh4)2[(CO)2(CN)Fe(,-ndt)Ni(,-ndt)Fe(CO)2(CN)] (4) were isolated. X-ray structural analyses of the trinuclear complexes revealed a Fe-Ni-Fe array in which the metal centers are connected by the ndt sulfur bridges and direct FeNi bonds. Hydrogen bonding between the CN ligand in 3 and cocrystallized ethanol was found in the solid-state structure. The monocyanide complex 3 and dicyanide complex 4 reacted with acids such as HOTf or HCl generating insoluble materials, whereas complex 1 did not react. [source] Highly Symmetrical Tetranuclear Cluster Complexes Supported by p - tert -Butylsulfonylcalix[4]arene as a Cluster-Forming LigandEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 9 2006Takashi Kajiwara Abstract Square-planar tetranuclear clusters [M4(L)(AcO)4(,4 -OH)], (M = MnII, CoII, and NiII) are synthesized using tetra-anionic p - tert -butylsulfonylcalix[4]arene (L4,) as a cluster-forming ligand. Three complexes are crystallographically isostructural, being crystallized in the triclinic crystal system with space group P. The calix[4]arene acts as a tetrakis fac -tridentate ligand through four phenoxo and four sulfonyl oxygen atoms to form square arrangement of four metal ions, which are further bridged by four chelating acetate ions and one hydroxo ion in a ,4 manner to complete the hexacoordination of each metal center. Although the whole molecule of each complex is crystallographically independent, the molecule is highly symmetrical with a pseudo-four-fold axis lying on the ,4 -OH, group. The tetranuclear clusters are stable enough to maintain the core structures even in highly dilute solution (,10 ,M), which was confirmed by mass spectroscopic study, however, bridging acetates were easily exchanged by other carboxylate chelates to form derivatives such as [M4(L)(BzO)4(OH)],. Metal,metal interactions were investigated by means of magnetic susceptibility, and it was revealed that both ferro- and antiferromagnetic interactions occur in the NiII complex depending on the bridging angles of Ni,O,Ni. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source] Inclusion of p -sulfonatothiacalix[4]arene and its metal complexesTHE CHEMICAL RECORD, Issue 3 2009Mingyan Wu Abstract As a new member of the water-soluble calixarene family, p -sulfonatothiacalix[4]arene possesses unique properties resulting from its inherent structural characteristics. In our recent research, we have investigated the self-assembly of bowl-like p -sulfonatothiacalix[4]arenes with or without transition-metal ions in the presence of suitable guests. We have obtained a series of compounds with different structural motifs, such as capsules, tetranuclear clusters, and molecular clefts. In addition, p -sulfonatothiacalix[4]arenes show good inclusion abilities and can capture different guests by utilizing their hydrophobic cavities through supramolecular interactions. Even when a cone-like conformation is fixed, the p -sulfonatothiacalix[4]arene can also splay its opposite aromatic rings apart to adjust its cone-like conformations from C4v to C2v and even lower symmetries. All of these show that it is a good candidate for the research of inclusion phenomena. © 2009 The Japan Chemical Journal Forum and Wiley Periodicals, Inc. Chem Rec 9: 155,168; 2009: Published online in Wiley InterScience (www.interscience.wiley.com) DOI 10.1002/tcr.200800033 [source] | ||||||||||