2-Pyrrplylthiones as Monoanionic Bidentate N,S-Chelators: Synthesis and Molecular Structure of 2-Pyrrolylthionato Complexes of Nickel(II), Cobalt(III) and Mercury(II)
Bruckner, C., Rettig, S.J., and David Dolphin
The metal-chelating ability of 2-pyrrolylthiones is described. The readily available ligands di-2-pyrrolyl thione, 2-thioacetylpyrrole, and 2-thiobenzoylpyrrole constitute examples of monoanionic ligands with N,S-donor atom sets, although di-2-pyrrolyl thione could theoretically also achieve chelation through an N,N-donor set. A square planar Ni(II) complex, an octahedral Co(III) complex, and a tetrahedral Hg(II) complex, with the di-2-pyrrolyl thionato chelate have been prepared, and their structures have been characterized by 1H NMR, UV-vis, MS, IR, elemental analysis, and single-crystal X-ray diffraction. Crystal data for C18H14N4NiS2•0.28H2O, trigonal, R3, a = 18.467(1) Å, b = 18.467(1) Å, c = 26.404(2) Å, V = 7797(1) Å3; Z = 18, R = 3.2%. Crystal data for C27H21CoN6S3•C3H6O (acetone), monoclinic, P21/n, a = 9.569(1) Å, b = 23.152(1) Å, c = 13.659(1) Å, β = 100.882(8)o, V = 2971.6(5) Å3, Z = 4, R = 4.3%. Crystal data for C18H14HgN4S2, triclinic, P , a = 8.443(2), b = 14.278(1) Å, c = 7.445(1) Å, α= 90.561(9)o, β = 97.64(1)Å, γ= 104.250(9)o, V = 861.3(2) Å3, Z = 2, R = 4.2%. The bond lengths and angles of these metal complexes are comparable to those of known N,S-chelates. A comparison of the structural parameters of the ligand in the metal complexes with those for the free ligand demonstrates the preorganization of the free ligand for complexation and demonstrates the spectator role of the noncoordinating pyrrolic unit. Chelation of Ni(II) by 2-thioacetylpyrrole and 2-thiobenzoylpyrrole to provide complexes and with structures analogous to complex is also described.