Treatment of [(eta(5)-C5Me5)Ir(eta(5)-C6H5O)][BF4] (1) with an excess of trialkylphosphine (PR3 = PMe3, PEt3, and PMe2Ph) affords the eta(4)-phenol tautomers [(eta(5)-C5Me5)Ir(eta(4)-exo-2-(PR3)C6H5O)][BF4] (2-4) in which the phosphine nucleophile adds regioselectively at C-2. The X-ray molecular structure of such a phenol tautomer complex [(eta(5)-C5Me5)Ir (eta(4)-exo-2-(PMe3)C6H5O)][BF4] (2) is reported. Complex 2 crystallizes in the triclinic space group P (1) over bar with a = 8.599(1) Angstrom, b = 9.0173(9) Angstrom, c = 14.448(3) Angstrom, alpha = 95.90(1)degrees, beta = 99.47(1)degrees, gamma = 99.20(1)degrees, and Z = 2. Oxidation of these eta(4)-dienone complexes 2-4 by iodine affords the related phosphine salts [(C6H4OH)-PR3][BF4] (5-7). and the starting iridium complex is recycled in the form of [(eta(5)-C5Me5)Ir(mu-I)I](2).I-2 (8) as confirmed by an X-ray analysis carried out on compounds 5 and 8. Complex 5 crystallizes in the monoclinic space group P2(1)/c with a = 10.593(6) Angstrom, b = 19.922(4) Angstrom, c = 11.909(3) Angstrom, beta = 106.83(4)degrees, and Z = 8. The structure of 8 can be viewed as an infinite chain of dimeric iridium [(eta(5)-C5Me5)Ir(mu-I)I](2) bridged by I-2 units. Complex 8 crystallizes in the monoclinic space group P2(1)/c with a = 15.533(3) Angstrom, b = 8.374(1) Angstrom, c = 23.541(4) Angstrom, beta = 100.89(4)degrees, and Z = 4.