The reaction of the molybdenum-molybdenum triple-bonded dimer (CO)(2)CpMo MoCp(CO)(2) (Cp = eta(5)-C5H5) with the triple-bonded dimetallynes (ArMMAriPr4)-M-iPr4 or (ArMMAriPr6)-M-iPr6 (Ar-iPr4 = C6H3-2,6-(C6H3-2,6-Pr-2(i))(2), Ar-iPr6 = C6H3-2,6-(C6H2-2,4,6-Pr-3(i))(2); M = Ge, Sn, or Pb) under mild conditions (<= 80 degrees C, 1 bar) afforded (ArM)-M-iPr4 MoCp(CO)(2) or (ArM)-M-iPr6 MoCp(CO)(2) in moderate to excellent yields. The reactions represent the first isolable products from a metathesis of two metal-metal triple bonds. Analogous exchange reactions with the single-bonded (CO)(3)CpMo-MoCp(CO)(3) gave ArM-MoCp(CO)(3) (Ar = Ar-iPr4 or Ar-iPr6; M = Sn or Pb). The products were characterized by NMR (H-1, C-13, Sn-119, or Pb-207), electronic, and IR spectroscopy and by X-ray crystallography.