The NMR study of inversion at the metal centre and ligand exchange processes of Hg II bis-chelates: X-ray crystal structure of [pyr(NC 6H 11- c)S] 2Hg

Abstract

Novel bis-chelate Hg II complexes with a series of 1-isopropyl-3-methyl-4-Naryl(alkyl)aminomethylene-5-thion(seleno)pyrazole derivatives (pyr(NR)X) 2Hg of type ( I) have been prepared. For the first time intramolecular reactions of tetrahedral inversion at the metal centre and degenerate ligand exchange reactions proceeding on the NMR timescale have been observed. The activation barrier of the inversion for the complex of type ( I) with R = C 6H 11-cyclo, X = S has been found by use of dynamic 1H NMR spectroscopy (500 MHz) to be 54.3 kJ mol −1. For a series of complexes ( I) the activation barriers against intermolecular ligand exchange processes lie in the range of 65–69 kJ mol −1. An X-ray study of ( I) (R = C 6H 11-cyclo, X = S) revealed a pseudo-tetrahedral bond configuration of mercury, while the sulphur atoms demonstrate a tendency toward linear alignment with the angle SHgS' of 141.0° (1).