Tris(triphenylphosphinegold) oxonium tetrafluoroborate, [(Ph(3)PAU)(3)O]BF4, catalyzes the rearrangement of 1,5-allenynes to produce cross-conjugated trienes. Experimental and computational evidence shows that the ene reaction proceeds through a unique nucleophilic addition of an allene double bond to 14 a cationic phosphinegold(l)-complexed phosphinegold(l) acetylide, followed by a 1,5-hydrogen shift.