engleski

Computational Analysis of the Stereochemistry of ML2 Metal Complexes With Bpa and Imda Ligands

Bis-tridentate metal complexes of flexible ligands with [M(A-X-A)2] structure can form three different geometric isomers: mer, trans-fac and cis-fac[1]. Stability of an isomer is influenced by many factors such as electronic and steric properties of the coordinating ligand, type of metal ion, possibility of forming non-covalent interactions, type of anion present and others. The influences of such factors on a formation of a specific isomer of ML2 complex are not fully described. Understanding the isomer preference in said systems is an important starting point in development of new complex compounds with desired form and properties [2, 3]. In this work, derivatives of tridentate ligands bis(2-pyridine-2-ylmethyl)amine (bpa) and 2, 2’- iminodiacetamide (imda) were prepared and their corresponding complexes with different salts of Zn(II), Cu(II), Ni(II) and Co(II). For the central donor atoms oxygen and sulfur were chosen and in the case of nitrogen and phosphorous -NPh- and - PPh- functional groups. The solid-state structures of prepared complexes were characterized by single-crystal X-ray diffraction, while the structures in solution were studied by NMR spectroscopy. The stoichiometry and the stereochemistry of these complexes, together with possible conformations of their substituents, were studied using the (SMD)/M05-2X/6-31+G(d) DTF computational approach to determine their relative stability to each other. Experimental and computational results were compared and preferences of some central donor atoms to form specific isomers of ML2 complexes were observed. One of our goals was to determine which factors lead to formation of cis-fac isomers, which could be in the case of nitrogen or phosphorous as central atoms used in the development of new asymmetric catalysts.

DFT ; Metal complexes

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