engleski

Influence of the non-coordinating alkyl chain type in N-alkylated iminodiacetamides on the stability and structure of their complexes with nickel(II) and cobalt(II)

Reactions of N-alkyliminodiacetamides (Meimda, Etimda, n-Primda, i-Primda, n-Buimda, i-Buimda and t-Buimda ; Me = methyl, Et = ethyl, n-Pr = n-propyl, i-Pr = isopropyl, n-Bu = n-butyl, i-Bu = isobutyl and t-Bu = tert-butyl) with nickel(II) and cobalt(II) nitrate in aqueous solutions resulted in complexes of the general formula [M(Rimda)2](NO3)2. Fourteen new complexes [Ni(Meimda)2](NO3)2 (1a), [Co(Meimda)2](NO3)2 (1b), [Ni(Etimda)2](NO3)2 (2a), [Co(Etimda)2](NO3)2 (2b), [Ni(n-Primda)2](NO3)2 (3a), [Co(n-Primda)2](NO3)2 (3b), [Ni(i-Primda)2](NO3)2 (4a), [Co(i-Primda)2](NO3)2 (4b), [Ni(n-Buimda)2](NO3)2 (5a), [Co(n-Buimda)2](NO3)2 (5b), [Ni(i-Buimda)2](NO3)2 (6a), [Co(i-Buimda)2](NO3)2 (6b), [Ni(t-Buimda)2](NO3)2 (7a) and [Co(t-Buimda)2](NO3)2 (7b) were prepared and characterized by infrared spectroscopy and thermal analysis (TG/DTA). Several were also characterized by single-crystal X-ray diffraction (1a, 1b, 3a, 3b, 5a, 5b, 6a and 7a). The octahedral coordination environment around the nickel(II) and cobalt(II) ions in the structures of the complexes consists of two O, N, O'-tridentate N-arylalkyliminodiacetamide ligands arranged in a fac-position, resulting in the formation of trans isomers in all cases. Hydrogen bonds link cations and anions in 3D networks with alternating layers of cations and anions. The molecular geometry and infrared spectra of these complexes were also studied by DFT calculations using the B3LYP/6-311G(d, p) computational model. The calculated spectra and molecular geometry agree well with the experimental results despite the extensive hydrogen bonding networks. The stability of the complex cation [M(Rimda)2]2+ (expressed in term of binding energy between the cation M2+ and two Rimda molecules in the gas phase) increases for both Ni(II) and Co(II) with rising length of the alkyl chain in the case of the ligands containing non-branched side-chains.

Nickel(II) and cobalt(II) ; Iminodiacetamide ; X-ray crystal structure ; DFT geometry and vibrational calculation

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