The Sonogashira cross coupling between the monocarborane cluster 12-ethynylmonocarba-closo-dodecaborate [CB11H11-12-CCH]- and bromoarenes under Pd catalysis has been developed, providing access to aryl carboranyl alkynes in yields of 42-95%. The transformations proceed under mild conditions and with high functional group tolerance using commercially available coupling partners. X-ray structural analyses and the identification of an unusual phosphonium zwitterion byproduct are reported as well.