Different outcomes in the reactions of WCl6 with carboxylic acids

Abstract The reactions of WCl6 with a selection of carboxylic acids were investigated by using dichloromethane as reaction medium. The addition of pyridine-3-carboxylic acid (niacin) to WCl6 gave [C5H4NHC(O)Cl][WOCl5], 1, in 75% yield via selective Cl/O interchange. WCl6 reacted with RCO2H (R = CH3, CBr3, CHCl2) in 1:2 ratio resulting in the formation of HCl and the respective acyl chlorides, RC(O)Cl. WOCl4(κ1-CH3CO2H), 2, was isolated from WCl6/CH3CO2H in 41% yield. The 1:2 reaction of WCl6 with CCl3CO2H proceeded with HCl release affording a mixture of WCl5(O2CCCl3), 3, and WCl4(O2CCCl3)2, 4. Compound 3 was isolated from WCl6/CCl3CO2H (1:1 ratio) in 60% yield. All the metal products were characterized by analytical and spectroscopic techniques. The crystal structure of 1 was ascertained by X-ray diffractometry. DFT calculations were carried out in order to shed light into structural, mechanistic and thermodynamic features.