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The crystal structure of trans-[Cr(en)2Br2]ClO4 (en = 1,2-ethanediamine) has been determined by a single-crystal X-ray diffraction study at 150 K. The complex crystallizes in the space group $$ P\overline{1} $$ of the triclinic system with two mononuclear formula units in a cell of dimensions a = 6.853(4), b = 8.109(5), c = 12.475(8) Å, α = 81.006(10)° , β = 77.005(10)° and γ = 74.981(10)°. The Cr atom is in a slightly distorted octahedral environment, coordinated by four nitrogen atoms of two en ligands and two bromine atoms in trans axial positions. The mean Cr–N(en) and Cr–Br bond lengths are 2.079(3) and 2.4743(10)Å, respectively. The five-membered rings are in stable gauche conformations with N1–Cr1–N2 and N3–Cr2–N4 angles of 82.81(11)° and 83.67(11)°, respectively. The crystal packing is stabilized by a network of N–H···O and N–H···Br hydrogen bonds. The infrared and electronic absorption spectra are consistent with the results of X-ray crystallography. The spectroscopic properties of the title complex are in good agreement with the result of X-ray crystallography, which shows that the chromium atom is in an octahedral environment, coordinated by two bidentate 1,2-ethanediamine ligands and two bromine atoms in trans positions.[Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Abstract  In the title compound, [Cu(C34H52N4)](ClO4)2, the Cu(II) ion has a square-planar coordination somewhat distorted towards tetrahedral geometry. The macrocyclic ligand adopts a less stable trans-I (RSRS) configuration. The two benzyl groups and two secondary amine H atoms are oriented towards the same side of the macrocyclic plane. The two six-membered rings are in slightly distorted chair and unsymmetrical twist-boat forms while both five-membered chelate rings are in the gauche conformation. The longer distances (2.050(4) and 2.035(4) Å) of Cu–N(tertiary) compared to 2.017(4) and 1.990(4) Å for Cu–N(secondary) may be due to the steric effects of the attached two benzyl groups on the tertiary N atoms. The crystal structure is stabilized by hydrogen bonds between secondary NH groups and O atoms of perchlorate counter-ions. Graphical Abstract  In the title compound, [Cu(C34H52N4)](ClO4)2, the Cu(II) ion has a square-planar coordination somewhat distorted towards tetrahedral geometry. The macrocyclic ligand adopts a trans-I configuration. The benzyl groups and secondary amine H atoms are oriented towards the same side of the macrocyclic plane. [ABSTRACT FROM AUTHOR]