Versatile Behaviour of the Cyclohexane-1,2-dione Bis(semicarbazone) Ligand in Mono- and Di-nuclear Metal Complexes

Article abstract of DOI:10.1039/DT9920003089

The chelating properties of cyclohexane-1,2-dione bis(semicarbazone) (H2chds) were considered by means of IR spectroscopy and the crystal structures of 3 1, 2*2H2O 2 and H2chds*H2O.The structure of 1 is triclinic, space group P<*>, with a = 13.616(2), b = 12.694(2), c = 11.537(2) Angstroem, α = 68.13(1), β = 63.37(1), γ = 70.01(1) deg, Z = 2 and R = 0.0778.The crystals of 2 are also triclinic, space group P<*>, a = 13.504(4), b = 13.221(5), c = 8.333(5) Angstroem; α = 98.00(3), β = 77.71(4), γ = 106.43(3) deg,Z = 2 and R = 0.0688.The H2chds*H2O molecule crystallizes in the space group P2₁/c with a = 7.350(1), b = 15.469(3), c = 10.270(3) Angstroem; β = 93.98(2) deg, Z = 4 and R = 0.0372.The behaviour of the ligand is different in each structure: in 1 nearly planar tetradentate and accommodated in the equatorial positions of pentagonal bipyramids; in 2 distorted-octahedral co-ordination is provided by two tridentate ligand molecules having ore urea group free.The free molecule is nearly planar with a different conformation: its arms are folded in such a way that an intramolecular N-H...N hydrogen bond is allowed.The structure of 1 is quite original: dimers are formed by means of two carbonylic bridges; the apices of the two polyhedra are occupied by two water molecules and a nitrate ion and one water molecule respectively.

Full text of DOI:10.1039/DT9920003089

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