CRYSTAL AND MOLECULAR STRUCTURES OF BIS(2,2,6,6-TETRAMETHYL-3-METHYLAMINOHEPTAN-5-ONATE) COPPER(II) AND NICKEL(II)
P. A. Stabnikov1, S. I. Dorovskikh1, N. V. Pervukhina1, L. G. Bulusheva1, G. B. Romanenko2
1Nikolaev Institute of Inorganic Chemistry, Siberian Branch, Russian Academy of Sciences, Novosibirsk, Russia
2Institute of the International Tomography Center, Siberian Branch, Russian Academy of Sciences, Novosibirsk, Russia
Keywords: copper(II) and nickel(II) chelates, crystal structure, steric effects
Abstract
Two bis-chelates M(tmih)2 (M = Cu(II), Ni(II), tmih = (CH3)3C(NCH3)CHCOC(CH3)3)- are synthesized and their crystal structures are determined using XRD (Bruker APEX-II diffractometer with a CCD detector, lMo Ka, lCu Ka, graphite monochromator, T = 240(2) K and 296(2) K): Cu(tmih)2 (I) (space group P21/c , a = 12.9670(8) Å, b = 18.4921(9) Å, c = 11.0422(6) Å, β = 93.408(4)°, V = 2643.1(3) Å3, Z = 4) and Ni(tmih)2 (II) (space group P21/c , a = 12.810(2) Å, b = 18.529(2) Å, c = 11.243(2) Å, β = 91.959(7)°, V = 2667.1(6) Å3, Z = 4). The complexes are isostructural; the coordination polyhedron of metal atoms is a flattened tetrahedron formed from two O atoms (Cu-O of 1.901(2) Å, 1.892(2) Å, Ni-O of 1.845(2) Å, 1.833(2) Å) and two N atoms (Cu-N of 1.976(3) Å, 1.972(3) Å, Ni-N of 1.911(2) Å, 1.920(2) Å) of the ligand; the chelate OMN angles (M = Cu(II), Ni(II)) are in the 87.4-93.1° range; the OMO and NMN angles are 162.2° and 167.2° in I, 171.1° and 173.2° in II. The complexes have the molecular structures formed from isolated molecules bonded by van der Waals interactions. Using a quantum chemical hybrid M06 method, the structures of copper(II) chelates with the H, CH3, CH2CH3, CH(CH3)2, and C(CH3)3 substituents at the nitrogen atom are calculated. Found that with a bulky substituent at the nitrogen atom, the formation of chelates is hindered due to the intraligand repulsion between the atoms of this substituent and the tert-butyl group.
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