The reaction of $CpMo(CO)_3-M^+(M^+,;Li^+,;Na^+,;K^+,;PPN^{+a})$ with allyl halide was performed and the details of its counterion effects and solvent effect was investigated under the pseudo-first order conditions. The kinetic data from this reaction were compared with those from the reaction of the same anion with benzyl halides in terms of their inverse counterion effects.