Crystal and molecular structures of bis(2,2,6,6-tetramethyl-3-methylaminoheptan-5-onate) copper(II) and nickel(II).

Two bis-chelates M( tmih) (M = Cu(II), Ni(II), tmih = (CH)C(NCH)CHCOC(CH)) are synthesized and their crystal structures are determined using XRD (Bruker APEX-II diffractometer with a CCD detector, λMo K, λCu K, graphite monochromator, T = 240(2) K and 296(2) K): Cu(tmih) ( I) (space group P2/ c, a = 12.9670(8) Å, b = 18.4921(9) Å, c = 11.0422(6) Å, β = 93.408(4)°, V = 2643.1(3) Å, Z = 4) and Ni(tmih) ( II) (space group P2/ c, a = 12.810(2) Å, b = 18.529(2) Å, c = 11.243(2) Å, β = 91.959(7)°, V = 2667.1(6) Å, 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, CH, CHCH, CH(CH), and C(CH) 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. [ABSTRACT FROM AUTHOR]