Complex kleinian groups and limit sets in<i>P</i>²

For Γ a lattice in PU(2,1), the isometries of the 2-complex ball naturally extend to an action in : we prove that the limit set of this action coincides with the complement of the ball in the projective space. We prove that the action is ergodic with respect to a certain measure. Also, we study other kinds of actions: for instance we construct an action whose limit set is the entire , but is not minimal although it is algebraically mixing.