Photochemistry of the complexes trans,cis-Ru(E) (E′) (CO) 2(iPr-DAB) (ECl, SnPh 3, PbPh 3, Mn(CO) 5, Re(CO) 5, Me;E′ (depending on E) = SnPh 3, PbPh 3, GePh 3, Mn(CO) 5, Re(CO) 5) was found to be strongly dependent on the combination and characters of the axial ligands E and E′. Except for Ru(Cl) (SnPh 3) (CO) 2(iPr-DAB) and Ru(Cl) (PbPh 3) (CO) 2(iPr-DAB) which are nearly unreactive, one of the Ru-E/E′ bonds is split homolytically upon irradiation into the lowest-energy absorption band of the complex. For Ru(SnPh 3) 2(CO) 2 (iPr-DAB), this reaction occurs from a thermally equilibrated 3σπ ∗ excited state with a rate constant of 2.3 × 10 5s −1 and a temperature-dependent quantum yield ( E n = 1450 cm −1). The unselective Ru&.zsbdnd; (40%) and Ru-Sn (40%) bond homolysis of Ru(SnPh 3) (GePh 3) (CO) 2-(iPr-DAB) follows the same mechanism. On the other hand, bond homolysis is much faster (⪢ 10 8s −1) for complexes which contain RuMe, RuMn or RuRe bonds. Bond homolysis in these species is highly selective, since only RuMe, RuMn and RuRe bond splitting was observed for Ru(Me) (SnPh 3) (CO) 2(iPr-DAB), Ru(SnPh 3) (Mn(CO) 5)(CO) 2(iPr-DAB), respectively. The photoproduced [Ru(E) (CO) 2(iPr-DAB)] radicals were detected by time resolved UV-Vis spectroscopy on a timescale 10 ns-100 μs. The [Ru(SnPh 3) (CO) 2(iPr-DAB)] radical was also characterised by EPR in the form of its adduct with PPh 3. Depending on the solvent used, they either dimerise or abstract a chlorine atom from the solvent to produce Ru(Cl) (E) (CO) 2(iPr-DAB).