Neutral transition metal complexes with the tridentate ligand 4-(5-methyl-4-imidazolyl)-3-thiabutanoic acid. A series of isostructural octahedral compounds

Abstract

The synthesis and spectroscopic properties of the iron, cobalt, nickel and copper complexes with the ligand 4-(5-methyl-4-imidazoly)-3-thiabutanoic acid (abbreviated Hitba) are described. The compound Co(itba) 2 ( A) crystallizes in the triclinic space group P1 with a=7.600(1), b=7.697(1), c=8.2696(5) Å, α=86.745(8),β=71.321(7), γ=69.538(12)°, V=428.5 Å 3, D x=1.65 g/cm 3 for Z=1. The compound Cu(itba) 2 ( B) crystallizes in the triclinic space group P1 with a=7.789(3), b=7.794(4), c=8.138(4) Å, α=71.448(4), β=86.905(4), η=67.805(4)°, V=432.4 Å 3, D x=1.66 g/cm 3 for Z=1. In both structures the metal ion is located on the inversion centre because of symmetry considerations. The non-hydrogens were located using Fourier methods and the structures were refined by least-squares methods to residual R w values of 0.089 ( A) and 0.050 ( B). The coordination geometry of the metal ion in both compounds A and B is octahedral with the donor atoms of the two ligands in mutual trans positions. The bond distances in the cobalt compound are significantly different from those in the Jahn-Teller distorted copper compound (CoN=2.109(7), CuN=1.986(3); CoO=2.065(6), CuO=1.988(2); CoS=2.501(2), CuS=2.7146(8)). The geometry of the cobalt ion can be described as a rather regular octahedron compared with the elongated octahedral copper structure. The obtained compounds M(itba) 2 are all isostructural according to their X-ray powder patterns and IR spectra, and all show remarkably strong ligand field spectra.