Cobalt(II) and nickel(II) complexes with nitrogen-sulfur tripod ligands. Crystal and molecular structure of the five-coordinate complex bromotris(2-tert-butylthioethyl)aminecobalt(II) hexafluorophosphate (NS 3Br donor set)

Abstract

The tripod ligands tris(2-alkylthioethyl)amine, with alkyl = ethyl, iso-propyl, and tert-butyl, give with cobalt(II) and nickel(II) halides high-spin complexes with formulae [MLX 2], [MLX]Y, and [MLX] 2[MX 4] (where X = Cl, Br, I; Y = BPh 4, PF 6). The nickel complexes are either six- or five-coordinate: the coordination number decreases as the bulkiness of the alkyl group bound to the sulfur is increased. All the cobalt complexes contain the five-coordinate cation [CoLX] +. The crystal and molecular structure of the [Co(NS 3-t-Bu)Br]PF 6 complex has been determined by standard X-ray methods, and refined to R = 0.061. The crystals are monoclinic, space group P2 1/n. The unit cell dimensions are: a = 27.420 (2), b = 11.923 (4), c = 17.082 (1) Å, β = 102.40 (1)°, Z = 8. The complex cation has a trigonal bipyramidal geometry with the nitrogen and bromine atoms at the apexes, and the three sulfur atoms in the equatorial plane. The tetrahedral distortion is relatively small (mean BrCoS angle = 98.5°), and similar to that found for the [Co (Me 6tren)Br]Br complex [Me 6tren = tris(2-dimethylaminoethyl)amine).