AU-IR AND HG-IR MIXED-METAL CARBONYL CLUSTERS - SYNTHESIS, CHARACTERIZATION, AND SOLID-STATE STRUCTURE OF [IR-6(CO)(15)(AUPPH(3))(2)] AND [IR-6(CO)(14)(HGCL)(2)](2-)

The neutral cluster [Ir-6(CO)(15)(AuPPh(3))(2)] has been obtained by r eaction of [Ir-6(CO)(15)](2-) with [AuPPh(3)](+). It crystallizes in t he triclinic space group P1 with cell constants a = 13.160(2) Angstrom , b = 13.714(4) Angstrom, c 18.266(3) Angstrom, alpha = 65.47(2)degree s, beta = 110.93(2)degrees, gamma = 112.07(1)degrees, V = 2699(2) Angs trom(3), and Z = 2. Data were collected at room temperature to a maxim um 2 theta = 54 degrees. The final discrepancy indices were R = 0.032 and R(w) = 0.034 for 7217 independent reflections with I > 3 sigma(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 AuPPh(3) unit spans one Ir-Au edge. The metal skeleton of C-1 symmetry is coordinated by twelve terminal and three edge-bridging carbonyl groups. The dianionic [Ir-6(CO)(14)(HgCl)(2)](2-) has been p repared from [Ir-6(CO)(15)](2-) and Hg2Cl2, HgCl2 + Hg, or HgCl2 in th e presence of Na2CO3. The salt [PPh(4)](2)[Ir-6(CO)(14)(HgCl)(2)] crys tallizes in the monoclinic space group Cc with cell constants a = 10.2 57(2) Angstrom, b = 46.848(4) Angstrom, c 14.639(3) Angstrom, beta = 1 07.83(2)degrees, V = 6696(4) Angstrom(3), and Z = 4. Data were collect ed at room temperature to a maximum 2 theta = 50 degrees. The final di screpancy indices were R = 0.037 and R(w) = 0.036 for 3619 independent reflections with I > 3 sigma(I). The metallic framework forms an octa hedron of iridium atoms bearing, on four non-adjacent faces, two mu(3) -HgCl fragments and two mu(3)-CO groups. The chemical shift of the Hg- 199 NMR was found at +1508 ppm, and suggests an anomalous oxidation st ate.