An experimental study of ligand exchange and bond insertion in the reactions of dimanganese carbonyl ions with alcohols in the gas phase

Abstract

The gas-phase reactions of dimanganese carbonyl ions (Mn 2(CO) n +; n = 1–5) with methanol have been studied with the use of Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometry. The predominant reaction of the Mn 2(CO) n + ions with up to four CO ligands involves the incorporation of methanol and the loss of one or more CO ligands, whereas the Mn 2(CO) 5 + ion reacts by the successive addition of two alcohol molecules. The efficiency of the overall reaction with methanol decreases with the number of CO ligands present in the manganese containing ion. In addition, the reactions of the Mn 2(CO) 4 + ion with ethanol and n-propanol have been examined and observed to be less efficient than the reaction with methanol. The efficiency of the reaction of the Mn 2(CO) 4 + ion with CD 3OH, C 2D 5OH or n-C 3D 7OH is significantly lower than of the reaction with the related unlabelled species revealing the occurrence of a significant isotope effect on the overall process. The primary product ions of the reactions of Mn 2(CO) 4 + with an alcohol react further with the formation of Mn 2(CO) n (ROH) 2 + ( n = 0–2) ions. These latter ions react with an alcohol molecule with the formation of collision complexes that expel a hydrogen or alkane molecule together with the CO ligands. Based upon experiments with CD 3OH, C 2D 5OH and n-C 3D 7OH, respectively, the loss of a hydrogen molecule is concluded to involve insertion into the O H bond, whereas alkane elimination is a result of insertion into the C O bond of the alcohol.