Coordination properties of the didentate N,O ligand 1-(2-hydroxyethyl)-3,5-dimethylpyrazole (HL). Crystal structure of and 2

Article abstract of DOI:10.1002/recl.19931120506

The didentate N,O donor ligand 1-(2-hydroxyethyl)-3,5-dimethylpyrazole (N-hed) renders two kinds of coordination compounds, viz. with M = Co, Ni, Cu, and Zn, , and in which the ligand is neutral, and 2 with X = Cl, Br, and NO3 in which the ligand N-hed is in its deprotonated form, viz. 1-(2-oxidoethyl)-3,5-dimethylpyrazole (N-oed).The crystal structure of shows it to be mononuclear, with the copper ion at a centre of symmetry.Monoclinic, space group P2₁/c, a = 7.8176(8), b = 14.93(2), c = 8.4076(8) Angstroem, β = 92.62(2) deg, Z = 2; R = 0.036 (R_w=0.038) for 2132 significant reflections.The copper(II) ion is in a tetragonal-distorted, elongated-octahedral environment of two trans pyrazole nitrogen atoms at 1.974(2) Angstroem, two trans hydroxyl oxygen atoms at 1.991(2) Angstroem, and two trans oxygen atoms of monodentate coordinated nitrate anions at 2.561(2) Angstroem.The structure is stabilized by strong intramolecular hydrogen bonds between the hydroxyl group of the coordinated ligand and an oxygen atom of the coordinated nitrate ion with a short O-O distance of 2.599(2) Angstroem.The metal ions in the compounds are octahedrally surrounded by two nitrogen and two oxygen atoms of the ligand and by two anion donor atoms (respectively O, N, or Cl).The crystal structure of 2 shows it to be dinuclear.Triclinic space group P<*>, a = 4.5213(6), b = 8.484(1), c = 13.052(7) Angstroem, α = 81.50(3), β = 85.79(4), γ = 77.79(2) deg, Z = 1, R = 0.148 (R_W = 0.224) for 1534 reflections.The copper ions are bridged by two oxo atoms of the deprotonated ligands with a Cu-Cu distance of 3.042(4) Angstroem.Each Cu(II)ion is in a distorted square-planar O2NBr environment.The compounds 2 are diamagnetic and EPR-silent.