Cationic rhodium complexes of certain nitrogen-containing ligands exhibit excellent activity in the addition of arylboronic acids to aldehydes. The counterion had a notable effect with the weakly coordinating carborane anion affording a highly active catalyst.
Moreau, C., Hague, C., Weller, A. S., & Frost, C. G. (2001). Rhodium-catalysed aryl transfer to aldehydes: Counterion effects with nitrogen containing ligands. Tetrahedron Letters, 42(39), 6957-6960. https://doi.org/10.1016/S0040-4039(01)01421-6