Ultrafast pump-probe spectroscopic studies have been performed on (C5Me5)(2)U-N=C(Ph)(CH2Ph) and (C5Me5)(2)Th-N=C(Ph)(CH2Ph) including, for the uranium complex, the first direct measurement of dynamics of electronic deactivation within a 5f-electron manifold. Evidence has been found for strong coupling between the electronic ground state and the f-electron manifold which dominates the dynamics of the excited states of the bis(ketimide) uranium complex. These also demonstrate strong singlet-f manifold coupling, which assists in the deactivation of the photoexcited state of the uranium complex, and provide information oil intersystem crossing and internal conversion processes in both complexes.