Synthesis, characterization and crystal structures of the first pentacoordinate nickel(II) complexes containing N,S-donor ligands

Abstract

By reaction of the hydroxo nickel complexes [Ni([12]aneN₃)(μ-OH)]²⁺₂ ([12]aneN₃ = 2,4,4-trimethyl-1,5,9-triazacyclododec-1-ene ([12]aneN₃-mc1) and its 9-methyl derivative ([12]aneN₃-mc2)) with heterocyclic-2-thiones in acetone, the pentacoordinate nickel(II) complexes [Ni([12]aneN₃)(LL′)]⁺ (LL′ = py2S (pyridine-2-thionate) 1, 5; pym2S (pyrimidine-2-thionate) 2, 6; bzimSH (benzimidazole-2-thionate) 3, 7; bztzS (benzothiazole-2-thionate) 4, 8) have been prepared. The X-ray diffraction study on 5, 6 and 7 shows that the thionate is bonded to nickel atom as chelating η²-N,S ligand, the nickel atom being in a distorted square pyramidal geometry. Complex 7 is the first structurally characterized example of a 1,3-benzimidazole-2-thionate derivative acting as a chelating ligand. The 2-D NOE technique (NOESY) allowed us to assign the isotropically shifted resonances due to coordinated thionates. Elemental analysis as well as IR and UV-VIS spectroscopic studies have also been used to aid structural characterization.