Au-Ir and Hg-Ir Mixed-Metal Carbonyl Clusters. Synthesis, Characterization, and Solid State Structure of [Ir6(CO)15(AuPPh3)2] and [Ir6(CO)14(HgCl)2]2-

The neutral cluster [Ir6(CO)15(AuPPh3)2] has been obtained by reaction of [Ir6(CO)15]2 with [AuPPh3]+. It crystallizes in the triclinic space group P1 with cell constants a = 13.160(2) Å, b = 13.714(4) Å, c = 18.266(3) Å, α = 65.47(2)°, β = 110.93(2)°, γ = 112.07(1)°, V = 2699(2) Å3, and Z = 2. Data were collected at room temperature to a maximum 2θ = 54°. The final discrepancy indices were R = 0.032 and Rw= 0.034 for 7217 independent reflections with I > 3σ (I). The structure was solved by direct methods. The iridium atoms of the cluster define an octahedral frame capped by one gold-phosphine group. The second AuPPh3 unit spans one Ir-Au edge. The metal skeleton of C1 symmetry is coordinated by twelve terminal and three edge-bridging carbonyl groups. The dianionic [Ir6(CO)14(HgCl)2]2- has been prepared from [Ir6(CO)15]2_ and Hg2Cl2, HgCl2 + Hg, or HgCl2 in the presence of Na2CO3. The salt [PPh4]2[Ir6(CO)14(HgCl2] crystallizes in the monoclinic space group Cc with cell constants a = 10.257(2) Å, b = 46.848(4) Å, c = 14.639(3) Å, β = 107.83(2)°, V = 6696(4) Å3, and Z = 4. Data were collected at room temperature to a maximum 2θ = 50°. The final discrepancy indices were R = 0.037 and Rw = 0.036 for 3619 independent reflections with I >3σ(I). The metallic framework forms an octahedron of iridium atoms bearing, on four non-adjacent faces, two μ3-HgCl fragments and two μ3-CO groups. The chemical shift of the 199Hg NMR was found at +1508 ppm, and suggests an anomalous oxidation state. © 1995, American Chemical Society. All rights reserved.