text: Before the 1990s, tetrafluoroborate (), hexafluorophosphate (), and  perchlorate () were considered weakly coordinating anions.  These species are now known to bind to strongly electrophilic metal centers. Tetrafluoroborate and hexafluorophosphate anions are coordinating toward highly electrophilic metal ions, such as cations containing Zr(IV) centers, which can abstract fluoride from these anions. Other anions, such as triflates are considered to be low-coordinating with some cations.