Nickel(II) complexes with tripodal ligands: synthesis, X-ray structural and spectroscopic studies

Abstract

The synthesis, X-ray crystal structures and electronic spectra of two nickel complexes with tripodal ligands are reported. The nickel(II) complex, [NiL¹(ClO₄)]ClO₄, with the ligands, tris{[2-(2-aminophenyl)-thio]ethyl}amine L¹ crystallizes as purple rectangular parallelopipeds in the monoclinic space group P2₁/a with a= 9.542(7), b= 28.231(13), c= 11.136(7)Å, β = 91.50(6)°, Z= 4, R= 0.058 and R'= 0.067 for 2782 reflections. The Ni atom is bound equatorially to two S and two N atoms from two arms of the tripod while the two axial positions are occupied by the bridgehead nitrogen and an oxygen from a perchlorate. The complex [NiL²][ClO₄]₂ with the ligand tris{[2-(2-aminoethyl)thio]ethyl}amine L² crystallizes as blue prisms in the monoclinic space group P2₁/n with a= 11.7923(9), b= 16.813(2), c= 12.716(1)Å, β = 109.567(7)°, Z= 4, R= 0.039 and R= 0.060 for 3354 reflections. All the three arms of the ligand are bound to the Ni^II providing a distorted-octahedral S₃N₃ donor set. Solution electronic spectra (in acetonitrile, dimethylformamide or dimethyl sulfoxide) of [NiL²][ClO₄]₂ indicate retention of the solid-state structure, whereas for [NiL¹(ClO₄)]ClO₄ bound perchlorate is released in acetonitrile and replaced by solvent.