Cobalt(II)
chloro complexation in N-methylformamide–N, N-dimethylformamide
mixtures |
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Authors: | K Fujii Y Matsumoto Y Kaieda D Kobayashi Y Umebayashi S Ishiguro |
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Institution: | (1) Department of Chemistry, Faculty of Science, Kyushu University, Fukuoka Japan, 812-8581, Hakozaki, Higashi-ku |
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Abstract: | Cobalt(II)
chloro complexation has been studied by titration calorimetry and spectrophotometry
in solvent mixtures of N-methylformamide
(NMF) and N,N-dimethylformamide
(DMF). It revealed that a series of mononuclear CoClnn
(2–n)+
(n=1–4) complexes are formed in the
mixtures of NMF mole fraction x
NMF=0.05
and 0.25, and the CoCl+, CoCl3
–
and CoCl4
2– complexes
in the mixture of x
NMF=0.5,
and their formation constants, enthalpies and entropies were obtained. As
compared with DMF, the complexation is markedly suppressed in the mixtures,
as well as in NMF. The decreasing formation constant of CoCl+
with the NMF content is mainly ascribed to the decreasing formation entropy.
DMF is aprotic and thus less-structured, whereas NMF is protic to form hydrogen-
bonded clusters. In DMF-NMF mixtures, solvent clusters in neat NMF are ruptured
to yield new clusters involving DMF, the structure of which depends on the
solvent composition. The entropy of formation of CoCl+
will be discussed in relation to the liquid structure of DMF, NMF and their
mixtures. |
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Keywords: | cobalt(II) chloro complexation liquid structureN-methylformamide– N N-dimethylformamide mixtures titration calorimetry and spectrophotometry |
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