The invention provides a novel composition for bleaching cellulose based materials, such as wood pulp and paper which includes using an effective amount of a source of an oxidant and an oxidatively stable bleach activator having structure (I) wherein Y1, Y3 and Y4 each represents a bridging group having zero, one, two or three carbon containing nodes for substitution, and Y2 is a bridging group having at least one carbon containing node for substitution. Each node contains a C(R), C(R1)(R2), or a C(R)2 unit. Each R may be H, alkyl, cycloalkyl, cylcoalkenyl, alkenyl, aryl, alkynyl, alkylaryl, halogen, alkoxy, or phenoxy, CH2CF3, CF3 and combinations thereof, or form a substituted or unsubstituted benzene ring, or together with a paired R substituent bound to the same carbon atom form a cycloalkyl or cycloalkenyl ring; M is a transition metal; Q is any counterion; and L is any labile ligand.