Ring reversal, sulphur inversion, and 1,3-metal shifts in sulphur-containing six-membered-ring complexes of chromium and tungsten carbonyls

Abstract

Complexes of the general formula [M(CO)₅L](M = Cr or W; L = [graphic omitted]H₂,[graphic omitted]H₂, and β-[graphic omitted]HME) have been prepared and studied by variable-temperature ¹H n.m.r. spectroscopy. Detailed computer syntheses of static and dynamic spectra indicate that the complexes exist in a number of conformations which are interconverted by fluxional processes. These processes are six-membered ligand ring reversal, pyramidal sulphur-atom inversion, and commutation of an M(CO)₅ moiety over three sulphur atoms via a 1,3-shift process. Accurate energy barriers (ΔG^‡) for all three processes have been calculated. It is interesting to note that only the β-[graphic omitted]HMe complexes undergo the 1,3-shift process at ambient temperature.