2-Pyrrolylthiones as Monoanionic Bidentate N,S-Chelators:  Synthesis and Molecular Structure of 2-Pyrrolylthionato Complexes of Nickel(II), Cobalt(III), and Mercury(II)

• Published in: Inorganic chemistry 2000-12, Vol.39 (26), p.6100-6106
• Main Authors: Brückner, Christian, Rettig, Steven J, Dolphin, David
• Format: Article
• Language: English
• Subjects: Chelating Agents - chemical synthesis; Chelating Agents - chemistry; Cobalt; Crystallography, X-Ray; Ligands; Mercury; Models, Molecular; Molecular Conformation; Molecular Structure; Nickel; Pyrroles - chemical synthesis; Pyrroles - chemistry; Structure-Activity Relationship; Thiones - chemical synthesis; Thiones - chemistry
• ISSN: 0020-1669; 1520-510X
• DOI: 10.1021/ic0004636

The metal-chelating ability of 2-pyrrolylthiones is described. The readily available ligands di-2-pyrrolyl thione (6), 2-thioacetylpyrrole (10), and 2-thiobenzoylpyrrole (11) constitute examples of monoanionic ligands with N,S-donor atom sets, although di-2-pyrrolyl thione (6) could theoretically also achieve chelation through an N,N-donor set. A square planar Ni(II) complex, 14, an octahedral Co(III) complex, 18, and a tetrahedral Hg(II) complex, 17, 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 14:  C18H14N4NiS2·0.28H2O, trigonal, R3̄, 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 18- mer :  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)°, V = 2971.6(5) Å3, Z = 4, R = 4.3%. Crystal data for 17:  C18H14HgN4S2, triclinic, P1̄, a = 8.443(2), b = 14.278(1) Å, c = 7.445(1) Å, α = 90.561(9)°, β = 97.64(1)°, γ = 104.250(9)°, 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 6 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 (10) and 2-thiobenzoylpyrrole (11) to provide complexes 12 and 13 with structures analogous to complex 14 is also described.