Non-coordinating anion

Complexes derived from non-coordinating anions have been used to catalyze hydrogenation, hydrosilylation, oligomerization, and the living polymerization of alkenes.

The popularization of non-coordinating anions has contributed to increased understanding of agostic complexes wherein hydrocarbons and hydrogen serve as ligands.

A revolution in this area occurred in the 1990s with the introduction of the tetrakis[3,5-bis(trifluoromethyl)phenyl]borate ion, B[3,5-(CF3)2C6H3]−4, commonly abbreviated as B(ArF)4− and colloquially called "BARF".

[citation needed] Polar solvents, such as acetonitrile, THF, and water, tend to bind to electrophilic centers, in which cases, the use of a non-coordinating anion is pointless.

[5] The neutral molecules that represent the parents to the non-coordinating anions are strong Lewis acids, e.g. boron trifluoride, BF3 and phosphorus pentafluoride, PF5.

Structure of the weakly coordinating anion [Al(OC(CF 3 ) 3 ) 4 ] − , [ 4 ] illustrating its high symmetry. Color code: green = F, red = O, blue = Al.
Crystal Structure of related acid
The crystal structure of the compound [H(Et 2 O) 2 ][B(C 6 F 5 ) 4 ],. [ 8 ] H atoms are omitted from the image. Color code: red = O, yellow = F, gray = C.