Thermolysis of the dimer [(C5Me5)IrH3]2 in neat thiophene in the presence of tert-butylethylene at 60-degrees-C gives the desulfurization cleavage product [(C5Me5)Ir]2(mu-S)(mu-1,2-eta2-3,4-eta2-C4H6). This butadiene complex crystallizes in monoclinic space group Cc (No. 9) with a = 8.828(8) angstrom, b = 14.132(3) angstrom, c = 37.889(10) angstrom, beta = 96.76(5)-degrees, Z = 8, and V = 4694.0(7.3) angstrom3. Use of thiophene-d4 gives a d4 product in which deuterium appears at all positions of the coordinated butadiene. Reaction of the butadiene complex with CO produces free butadiene and the complex [(C5Me5)Ir(CO)]2(mu-S). The dicarbonyl complex crystallizes in monoclinic space group C2/c (No. 15) with a = 11.404(5) angstrom, b = 13.927(4) angstrom, c = 14.047(3) angstrom, beta = 97.34(2)-degrees, Z = 4, and V = 2212.8(2.1) angstrom3. Reaction of the butadiene complex with H-2 produces butane.