Steric interaction of solvation and sterically enhanced halogeno complexation of manganese(II), cobalt(II) and nickel(II) ions in N,N-dimethylacetamide
- Tokyo Institute of Technology, Yokohama (Japan)
- Kyushu Univ., Fukuoka (Japan)
The complexation of manganese(II), cobalt(II) and nickel(II) with bromide ions has been studied in N,N-dimethylacetamide (DMA) by calorimetry and spectrophotometry. The formation of [MBr]{sup +}, [MBr{sub 2}] and [MBr{sub 3}]{sup -} (M = Mn, Co, Ni) was revealed in all the metal systems. Interestingly, the complexation is significantly enhanced in DMA over N,N-dimethylformamide (DMF). This is unusual because physicochemical properties of DMA and DMF as solvent are similar. Furthermore, extracted electronic spectra of individual complexes of Ni{sup II} suggested the presence of a geometry equilibrium, [NiBr(DMA){sub 5}]{sup +} = [NiBr(DMA){sub 4}]{sup +} + DMA, in DMA. A similar geometry equilibrium is also suggested, [NiBr{sub 2}(DMA){sub 3}] = [NiBr{sub 2}(DMA){sub 2}] + DMA. Such geometry equilibria were not observed in DMF. With regard to cobalt(II), electronic spectra show the presence of the four-coordinated [CoBr(DMA){sub 3}]{sup +} complex in DMA, unlike the six-coordinated [CoBr(DMF){sub 5}]{sup +} one in DMF. These facts suggest that a specific strong steric interaction operates between coordinating solvent molecules, which plays a key role in the complexation behavior of the divalent transition metal ions in DMA.
- Sponsoring Organization:
- USDOE
- OSTI ID:
- 171884
- Journal Information:
- Journal of Solution Chemistry, Journal Name: Journal of Solution Chemistry Journal Issue: 12 Vol. 23; ISSN 0095-9782; ISSN JSLCAG
- Country of Publication:
- United States
- Language:
- English
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