High-nuclearity close-packed palladium-nickel carbonyl phosphine clusters:Heteropalladium [Pd16Ni4(CO)(22)(PPh3)(4)](2-) and [Pd33Ni9(CO)(41)(PPh3)(6)](4-) containing pseudo-T-d ccp Pd16Ni4 and pseudo-D-3h hcp Pd33Ni9 cores

[Pd16Ni4(CO)(22)(PPh3)(4)](2-) (1) and [Pd33Ni9(CO)(41)(PPh3)(6)](4-) (2) w ere obtained as the two major products from the reduction of PdCl2(PPh3)(2) with [Ni-6(CO)(12)](2-). Their crystal structures as [PPh4](+) salts were unambiguously determined from CCD X-ray crystallographic analyses, the resu lting stoichiomotries were ascertained from elemental analyses. Infrared, m ultinuclear H-1, P-31{H-1} NMR, UV-vis, CV, variable-temperature magnetic s usceptibility, and ESI FT/ICR mass spectrometric measurements were performe d. The Pd16Ni4 core Of 1 ideally conforms to a ccp nu (3) tetrahedron of ps eudo-T-d (43m) symmetry. Its geometry normal to each tetrahedral Pd7Ni3 fac e (i.e., along each of the four 3-fold axes) may be viewed as a four-layer stacking of 20 metal atoms in a ccp [a(Ni-1) b(Pd-3) c(Pd-6) a(Pd7Ni3)] seq uence. A comparative analysis of the different ligand connectivities about the analogous metal-core geometries in 1 and the previously reported [Os-20 (CO)(40)](2-) has stereochemical implications pertaining to the different p ossible modes of carbon monoxide attachment to ccp metal(III) surfaces. The unique geometry of the Pd33Ni9 core of 2, which has pseudo-Dsi, (62m) symm etry, consists of five equilateral triangular layers that are stacked in a hcp [a(Pd7Ni3) b(Pd-6) a(Pd7Ni3) b(Pd-6) a(Pd7Ni3)] sequence. Variable-temp erature magnetic susceptibility measurements indicated both 1 and 2 to be d iamagnetic over the entire temperature range from 5.0 to 300 K. Neutral Pd- 12(CO)(12)(PPh3)(6) (3) and [Pd-29(CO)(28)(PPh3)(7)](2-) (4) as the [PPh4]( +) salt were obtained as minor decomposition products from protonation reac tions of 1 and 2, respectively, with acetic acid. Compound 3 of pseudo-D-3d (32/m) symmetry represents the second highly deformed hexacapped octahedra l member of the previously established homopalladium family of clusters con taining uncapped. monocapped. bicapped, and tetracapped Pds octahedra. The unprecedented centered 28-atom polyhedron for the Pd-29 core of 4 of pseudo -C-3 nu, (3m) symmetry may be described as a four-layer stacking of 29 meta l atoms in a mixed hcp/ccp [a(Pd-1) b(Pd-3) a(Pd-10) c(Pd-15)] sequence.