Mechanism of the gas phase reactions of the C5H5Ni+ and C5H5Co+ ions with substituted pyridines. A combined experimental and theoretical study

Different products have been observed in the reactions ofC5H5Co+ andC5H5Ni+ ions with halogen-substituted pyridines (XPy) that have been studied by ion trap mass spectrometry (ITMS) techniques.In particular,an addition product C5H5M(XPy)+and a product ion C5H4M(Py)+ corresponding to a loss of a HX molecule(X =F,Cl,Br)havebeen detected. Acomputational study at the DFT level on model-systems formed by 2-fluoro and 2-bromopyridine reacting either with the C5H5Ni+ or the C5H5Co+ ion has been carried out. This study shows the existence of a general mechanistic pattern. The rate-determining step of this mechanism is the migration of the halogen from the pyridine ring to the metal. A final hydrogen abstraction step carried out by the halogen leads to the expulsion of a HX molecule.