Pantalon Juraj, Natalija; Miletić, Goran I.; Perić, Berislav; Popović, Zora; Smrečki, Neven; Vianello, Robert; Kirin, Srećko
(2019)
Stereochemistry of Hexacoordinated Zn(II), Cu(II), Ni(II) and Co(II) Complexes with Iminodiacetamide Ligands.
Inorganic Chemistry, 58
(24).
pp. 16445-16457.
ISSN 0020-1669
Abstract
Metal complexes of iminodiacetamide (imda) ligands and metal ions Zn(II), Cu(II), Ni(II) and Co(II) were prepared, using eight imda ligands (L1-L8) substituted with groups of different steric and electronic properties on the central amine nitrogen atom (hydrogen atom, methyl, isopropyl, benzyl) and the para-position of phenyl rings (nitro, dime-thylamino). The effect of these substituents on the stoichiometry (ML, ML2), geometry and stereochemistry (mer, trans-fac, cis-fac) of the complexes was studied in solid state, in solution and by DFT calculations. X-Ray single crystal and powder diffraction, thermogravimetry, and IR spectroscopy showed that in the solid state imda ligands preferen-tially form trans-fac ML2 complexes, with the exception of the cis-fac complex 7Zn. NMR spectroscopy of diamagnetic Zn(II) and paramagnetic Co(II) complexes revealed the formation of both ML and ML2 complexes in solution, which was also confirmed by UV-Vis titrations. Variable temperature NMR was used to study the effect of the substituent on the central amine nitrogen on the Zn─N bond strength and nitrogen inversion. Relative stabilities of isomers were rationalized by computations and the optimized structures used for the geometry analysis.
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