Ionic fragmentation versus electron detachment in isolated transition metal complex dianions

Gas-phase multiply charged anions represent highly energetic species that are susceptible to decay by electron detachment or fragmentation into two ions. The relative activation barriers for decay via these channels have been investigated for IrCl 6 2 - , OsCl 6 2 - , ReCl 6 2 , IrBr 6 2 - and PtBr 6 2 - using collisional excitation of ions isolated within a quadrupole trap. All of the dianions decayed via ionic fragmentation, demonstrating that the repulsive Coulomb barrier (RCB) for ionic fragmentation lies below the RCB for electron detachment. Our results indicate that ionic fragmentation will represent the preferred lowest energy decay pathway for these, and other, dianions that can dissociate to form stable anions.