The mono- and bis-(metal pentacarbonyl) complexes [{;M(CO) 5}; m {;MeS(CH 2S) n Me};] (M = Cr, W; m = 1, n = 2; m = 2, n = 2,3) have been synthesised and studied by dynamic NMR methods. Total band shape fitting of temperature variable 1H NMR spectra of the complexes has enabled the determination of very accurate data for pyramidal ligand atom sulphur inversions. At higher temperatures line shape changes that would accord with 1,3 intramolecular shifts of the M(CO) 5 moieties between ligand sulphur atoms were observed. Concurrent dissociation, however, prevented access to the high quality spectra required for accurate determination of kinetic data of such shifts.