RhCl3 is shown to mediate unusual coupling reactions of tert-butyl acetylene. When RhCl3(H2O)n was heated with four equivalents of tert-butyl acetylene in methanol, the dinuclear complex [{Rh(μ-Cl)(CH2tBu)(tBuC=CHCOCH2tBu)}2] (2) was isolated. A larger excess of tert-butyl acetylene (12 equiv.) resulted in the formation of the dimer [{η5-C5H2tBu2(CH2tBu)}Rh(μ-Cl)3Rh(C24H42O2)] (3). Both complexes were analyzed by single-crystal X-ray diffraction.