The complex [(eta(5)-C(5)Me(5))Ir(C2H4)(p-N(2)C(6)H(4)OMe)][BF4] (1) reacts with X(-) = I- and Br- to give neutral [(eta(5)-C(5)Me(5))IrX](2)(mu-eta(2)-p-N(2)C(6)H(4)OMe)(mu-eta(1)-p-N(2)C(6)H(4)OMe) where X = I (2) and Br (3), respectively. The spectroscopic data for 2 and 3, as well as their N-15(alpha) derivatives 2a and 3a, establish that 2 and 3 are isostructural in solution and each contains diiridium centers that are bridged by two coordinatively different aryldiazenido ligands, i.e., mu-eta(2)- and mu-eta(1)-p-N(2)C(6)H(4)OMe groups. This structural feature has also been unequivocally confirmed in the solid state by a single-crystal X-ray crystallographic analysis of 2. The NMR studies of the protonation reactions of 2a and 3a indicate that protonation occurs solely at the N-alpha atom of the mu-eta(2)-p-N(2)C(6)H(4)OMe ligand in both cases. When 1 reacts with the metal base complex (eta(5)-C(5)Me(5))Ir(CO)(2) in ethanol at reflux, the monobridging aryldiazenido complex [{(eta(5)-C(5)Me(5))Ir(CO)}(2)(mu-eta(2)-p-N(2)C(6)H(4)OMe][BF4] (6) results. The molecular structure of 6 in the solid state, established by a single-crystal X-ray crystallographic analysis, is consistent with its spectroscopic properties in solution. On the basis of an EHMO calculation and a fragment orbital interaction analysis, a rationale is suggested to explain how the electronic nature of the substituent ligand influences the outcome of substitution reactions of 1. Complex 2 crystallized in the space group with a = 8.937(2) Angstrom, b = 10.036(2) Angstrom, c = 10.893(2) Angstrom, a = 79.98(1)degrees, beta 79.52(1)degrees, gamma = 70.36(1)degrees, and Z = 1. The structure of 2 was refined to R(F) = 0.021 and R(wF) = 0.029 on the basis of 3077 observed independent reflections with I-o greater than or equal to 2.5 sigma(I-o) and 189 variables in the range 28 = 4-52 degrees. Complex 6 crystallized in the space group Pc2lb with a = 8.821(1) Angstrom, b = 20.237(2) Angstrom, c = 34.808(5) Angstrom, and Z = 8. The structure of 6 was refined to R(F) = 0.044 and R(wF) = 0.049 on the basis of 1661 observed independent reflections with I-0 greater than or equal to 2.5 sigma(I-0) and 259 variables in the range 2 theta = 4-50 degrees.