IRIDIUM CARBONYL CLUSTERS .2. CRYSTAL-STRUCTURE AND MOLECULAR-GEOMETRY OF IR4(CO)11[CN(TERT-BU)], A DERIVATIVE OF IR4(CO)12 WITH NO BRIDGING CARBONYL LIGANDS

The title complex has been characterized structurally by means of a single-crystal X-ray diffraction study. It crystallizes in the centrosymmetric monoclinic space group P21/c with a = 13.503 (2) Å, b = 14.358 (2) Å, c = 12.421 (2) Å, ² = 97.07 (1)μ, V= 2389.8 (6) Å3, and p(calcd) = 3.22 g cm-3 for mol wt 1160.13 and 2 = 4. Diffraction data were collected with a Syntex P21 automated four-circle diffractometer, and the structure was solved by conventional Patterson, difference Fourier, and full-matrix least-squares refinement techniques. The resulting discrepancy indices were RF = 7.2% and RWF = 4.7% for all 3146 independent reflections (3° < 2θ < 45°; Mo Ka radiation) and RF = 4.9% and RWF = 4.3% for those 2473 data with I > 3<r(I). The four iridium atoms define a tetrahedron. The isocyanide ligand occupies a site on Ir(4), the Ir-CN(t-Bu) bond length being 1.976 (19) Å. Ir-CO distances range from 1.80 (3) to 1.92 (3) Å. There are slight variations in Ir-Ir distances within the tetrahedral cluster. Distances involving the unique Ir(4) average 2.681 [2] Å and are slightly shorter than the other [(OC)3Ir-Ir(CO)3] bond lengths, which average 2.689 [2] Å. © 1979, American Chemical Society. All rights reserved.