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Discussion of Planarity of Molecular Structures Using Novel Pentanuclear Cu/Ni Complexes as an Example

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posted on 06.06.2012, 00:00 by Elena A. Buvaylo, Oksana V. Nesterova, Vladimir N. Kokozay, Olga Yu. Vassilyeva, Brian W. Skelton, Roman Boča, Dmytro S. Nesterov
Two novel heterometallic complexes, [Cu2Ni3(NCS)4(Me2Ea)6] (1) and [Cu2Ni3Cl4(Me2Ea)6] (2) (HMe2Ea = 2-dimethylaminoethanol), have been prepared using a one-pot reaction of copper powder with nickel thiocyanate (1) or chloride (2) in an acetonitrile solution of HMe2Ea in air. The magnetic investigations disclose dominant ferromagnetic exchange interactions with S = 4 and 2 ground states for 1 and 2, respectively. A planar arrangement of five metal centers in both compounds inspired us to study the question of planarity of polynuclear coordination compounds having MaXb cores (where M = metal and X = bridging atom). The distribution, obtained by the searches via the Cambridge Structural Database, of the structures possessing a planar disposition of the metal centers, depending on their nuclearity, is discussed, and typical planar molecular structure types (MST) are identified. It is demonstrated that the relative amounts of planar structures obey exponential decay in the 3–8 nuclearity region, with the exception of heptanuclear structures. The factors that influence the disposition (planar or nonplanar) of metal centers in the MaXb molecular structure types are selected. Finally, we offer a model for general description of MSTs by the graph theory toward the design of high-nuclear coordination compounds.