Crystal structures and coordination-site exchange reactions of palladium(II) and platinum(II) complexes containing tris[2-(tert-butylthio)ethyl]amine

Palladium(II) and platinum(II) complexes, [PdX((NS3Bu)-Bu-1)]BPh4 (X = Cl, Br, I; (NS3Bu)-Bu-1 = tris[2-(tert-butylthio)ethyl]amine) and [PtCl((NS3Bu) -Bu-1)]BPh4, were prepared, and their structures were determined by X-ray a nalyses. The geometry around the palladium and platinum atoms is square pla nar. The NS:Bu ligand functions as a tridentate ligand and one sulfur atom is not coordinated to the metal. The H-1 NMR spectrum of [PdCl((NS3Bu)-Bu-1 ]BPH4 in acetone-d(6) exhibited a dynamic behavior. At 20 degreesC the spec trum showed a singlet signal at 1.60 ppm that can be assigned to tert-butyl protons, whereas at - 70 degreesC three singlet signals were observed at 1 .36, 1.61, and 1.70 ppm with an intensity ratio of 1: 0.25: 2. The signals at 1.36 and 1.70 ppm are assigned to the tert-butyl protons in the square-p lanar structure, and these signals are consistent with the X-ray structure. The signal at 1.61 ppm can be assigned to the tert-butyl protons in a trig onal-bipyramidal structure where the three tert-butyl groups are magnetical ly equivalent. Thus, we concluded that the coordination-site exchange occur red via a trigonal-bipyramidal intermediate. The square-planar and trigonal -bipyramidal species of [PdCl((NS3Bu)-Bu-1)]BPh4 are in equilibrium in acet one-d(6). The equilibrium was shifted toward the square-planar species on d ecreasing the temperature. The H-1 NMR spectra for [PdX((NS3Bu)-Bu-1)]BPh4 (X = Cl, Br, and I) were similar to one another at the same temperature, su ggesting that the site-exchange process is insensitive to the kind of coexi sting halogen ligand. The site exchange reaction of [PtCl((NS3Bu)-Bu-1)]BPh 4 seems to occur more slowly than that of the palladium(II) analogue. (C) 2 001 Elsevier Science B.V. All rights reserved.