Ruthenium diimine complexes, Ru(L) 3 2 + (L=bipy=2,2'-bipyridine or phen=1,10-phenanthroline), were formed in the gas phase by electrospray ionization and accelerated through a 50-kV electrostatic potential. In collisions between Ru(L) 3 2 + and O 2 , fragment ions were produced in addition to Ru(L) 3 + and Ru(L) 3 3 + formed in collisional electron transfer. Cross-sections for the electron stripping and electron capture reactions are 10+/-0.2A 2 and 1.7+/-0.1A 2 , respectively, for L=bipy and 3.8+/-0.2A 2 and 0.8+/-0.1A 2 , respectively, for L=phen. In collisions between Ru(L) 3 2 + and Na electron capture was the major reaction channel and resulted in Ru(L) 3 + as well as Ru(L) 3 - (as a result of multiple-collision conditions). Cross-sections are of the order of 100A 2 for the formation of one-electron reduced Ru(L) 3 + ions. The kinetic energy released by the dissociation of Ru(L) 3 2 + and Ru(L) 3 3 + into Ru(L) 2 + / 2 + and L + after collisional activation was measured to be 1.5eV for Ru(bipy) 3 2 + , 3.7eV for Ru(phen) 3 2 + , 8eV for Ru(bipy) 3 3 + , and 6eV for Ru(phen) 3 3 + .