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Title
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The hexakis(N,N '-dimethylurea)cobalt(II) cation : a flexible building block for the construction of hydrogen bonded networks
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Author
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Abstract
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| The ligand N,N'-dimethylurea (DMU) is used to propagate the octahedral coordination geometry of [Co(DMU)(6)](2+) into 1D and 2D assemblies via a combination of coordinative bonds and interionic hydrogen-bonding. Compounds [Co(DMU)(6)](ClO4)(2) (1), [Co(DMU)(6)](BF4)(2) (2) and [Co(DMU)(6)](NO3)(2) (3) have been prepared from the reactions of DMU and the appropriate hydrated cobalt(II) salts in EtOH, MeCN or Me2CO (only for 1) in the presence of 2,2-dimethoxypropane. Crystal structure determinations demonstrate the existence of [Co(DMU)(6)](2+) cations and ClO4- BF4- or NO3- counterions. The great stability of the [Co(DMU)(6)](2+) cation in the solid state is attributed to a pseudochelate effect which arises from the existence of strong intracationic N-H...O(DMU) hydrogen bonds. The [Co(DMU)(6)](2+) cations and counterions self-assemble to form a hydrogen-bonded 1D architecture in 1, and different 2D hydrogen-bonded networks in 2 and 3. The precise nature of the resulting supramolecular structure is influenced by the nature of the counterion. Two main motifs of intermolecular (interionic) hydrogen bonds have been observed: N-H...O(ClO4-, NO3-) or N-H...F(BF4-) and weak C-H...F(BF4-) or C-H...O(NO3-) hydrogen bonds. The complexes were also characterized by vibrational spectroscopy (IR, far-IR, low-frequency Raman). The spectroscopic data are discussed in terms of the nature of bonding and the known structures. |
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Language
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English
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Source (journal)
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Zeitschrift für Naturforschung: B: a journal of chemical sciences. - Tübingen
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Publication
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Tübingen
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2003
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ISSN
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0932-0776
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Volume/pages
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58
:1
(2003)
, p. 74-84
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ISI
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000181892500010
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Full text (publisher's version - intranet only)
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