Nanosized (μ₁₂-Pt)Pd_164-xPt_x(CO)₇₂(PPh₃)₂₀(x≈ 7) Containing Pt-Centered Four-Shell 165-Atom Pd−Pt Core with Unprecedented Intershell Bridging Carbonyl Ligands:  Comparative Analysis of Icosahedral Shell-Growth Patterns with Geometrically Related Pd₁₄₅(CO)_x(PEt₃)₃₀(x≈ 60) Containing Capped Three-Shell Pd₁₄₅Core

Abstract

Presented herein are the preparation and crystallographic/microanalytical/magnetic/spectroscopic characterization of the Pt-centered four-shell 165-atom Pd-Pt cluster, (mu(12)-Pt)Pd(164-x)Pt(x)(CO)(72)(PPh(3))(20) (x approximately 7), 1, that replaces the geometrically related capped three-shell icosahedral Pd(145) cluster, Pd(145)(CO)(x)(PEt(3))(30) (x approximately 60), 2, as the largest crystallographically determined discrete transition metal cluster with direct metal-metal bonding. A detailed comparison of their shell-growth patterns gives rise to important stereochemical implications concerning completely unexpected structural dissimilarities as well as similarities and provides new insight concerning possible synthetic approaches for generation of multi-shell metal clusters. 1 was reproducibly prepared in small yields (<10%) from the reaction of Pd(10)(CO)(12)(PPh(3))(6) with Pt(CO)(2)(PPh(3))(2). Its 165-atom metal-core geometry and 20 PPh(3) and 72 CO ligands were established from a low-temperature (100 K) CCD X-ray diffraction study. The well-determined crystal structure is attributed largely to 1 possessing cubic T(h) (2/m3) site symmetry, which is the highest crystallographic subgroup of the noncrystallographic pseudo-icosahedral I(h) (2/m35) symmetry. The "full" four-shell Pd-Pt anatomy of 1 consists of: (a) shell 1 with the centered (mu(12)-Pt) atom encapsulated by the 12-atom icosahedral Pt(x)Pd(12-x) cage, x = 1.2(3); (b) shell 2 with the 42-atom nu(2) icosahedral Pt(x)Pd(42-x) cage, x = 3.5(5); (c) shell 3 with the anti-Mackay 60-atom semi-regular rhombicosidodecahedral Pt(x)Pd(60-x) cage, x = 2.2(6); (d) shell 4 with the 50-atom nu(2) pentagonal dodecahedral Pd(50) cage. The total number of crystallographically estimated Pt atoms, 8 +/- 3, which was obtained from least-squares (Pt(x)/Pd(1-x))-occupancy analysis of the X-ray data that conclusively revealed the central atom to be pure Pt (occupancy factor, x = 1.00(3)), is fortuitously in agreement with that of 7.6(7) found from an X-ray Pt/Pd microanalysis (WDS spectrometer) on three crystals of 1. Our utilization of this site-occupancy (Pt(x)Pd(1-x))-analysis for shells 1-3 originated from the microanalytical results; otherwise, the presumed metal-core composition would have been (mu(12)-Pt)Pd(164). [Alternatively, the (mu(12)-Pt)M(164) core-geometry of 1 may be viewed as a pseudo-Ih Pt-centered six-shell successive nu(1) polyhedral system, each with radially equivalent vertex atoms: Pt@M(12)(icosahedron)@M(30)(icosidodecahedron)@M(12)(icosahedron)@M(60)(rhombicosidodecahedron)@M(30)(icosidodecahedron)@M(20)(pentagonal dodecahedron)]. Completely surprising structural dissimilarities between 1 and 2 are: (1) to date 1 is only reproducibly isolated as a heterometallic Pd-Pt cluster with a central Pt instead of Pd atom; (2) the 50 atoms comprising the outer fourth nu(2) pentagonal dodecahedral shell in 1 are less than the 60 atoms of the inner third shell in 1, in contradistinction to shell-by-shell growth processes in all other known shell-based s...

Syntheses, structures and properties of primarily nanosized homo/heterometallic palladium CO/PR 3 -ligated clusters

“…Two exceptional multi-shell clusters Pd 145 (CO) x (PEt 3 ) 30 , x ∼ 60 (Tran et al 2000b) and (m 12 -Pt)Pd 164−x Pt x (CO) 72 (PPh 3 ) 20 (x ∼ 7) (Mednikov et al 2007b) were isolated and their icosahedral multi-shell polyhedra unambiguously established by X-ray crystallography. The Pd 145 cluster was originally obtained from the reaction of Pd(PEt 3 ) 2 Cl 2 with Au(PPh 3 )Cl and later in higher yield • C. The similar geometries of the first three shells in these M 145 and M 165 clusters are composed of a centred icosahedron (m 12 -M)M 12 that is encapsulated by a 42-atom n 2 icosahedron, which in turn is surrounded by a 60-atom rhombicosidodecahedral cage (vide infra).…”

Small Adsorbate‐Assisted Shape Control of Pd and Pt Nanocrystals

“…Many metallic Pd and Pt nanoclusters are able to crystallize into single crystals for total structure determinations. [113][114][115][116][117][118][119][120] Nanocluster chemistry could provide us important information on the adsorption structure of small adsorbates on the metal surface as well as the structure of nanocrystals at the very beginning of the control process. In the synthesis of nanocrystals, such information is usually hard to be acquired but critical to deeply understand how small adsorbates control the formation of nanocrystals.…”

Nanopartikuläre Funktionsmaterialien

“…[279] Schließlich können Hohlkugeln als medizinische Kontrastmittel oder zum Transport und zur gezielten Freisetzung von Medikamenten eingesetzt werden. [280] In 30 ] mit x % 60) [284] und Hauptgruppenmetallen (z. B.…”