Nanosized Pd145(CO)x(PEt3)30 Containing a Capped Three-Shell 145-Atom Metal-Core Geometry of Pseudo Icosahedral Symmetry

Abstract

Presented herein are the geometrical features of a stoichiometric capped three-shell palladium carbonyl phosphane cluster 1. Its pseudo I h metal core (see Figure 1) consists of a central Pd atom surrounded by 12 Pd atoms (shell 1), which in turn are encapsulated by 42 Pd atoms (shell 2), which in turn are encapsulated by 60 Pd atoms (shell 3). Thirty additional Pd atoms cap the 30 square polygons of the third-shell polyhedron with a triethylphosphane ligand attached to each capping Pd atom. It is currently presumed that 60 CO groups (crystal-disordered) edge-bridge the 30 capping Pd atoms with one-half of the square basal Pd atoms (in accordance with an IR carbonyl spectrum). The diameter of the entire Pd 145 core of 1 between two centrosymmetrically opposite capping Pd atoms is 1.65 nm; the spherical-like geometry of the centered three-shell Pd 115 kernel (that is, without the 30 capping Pd atoms) is evidenced by the similarity of the corresponding distances for the centrosymmetrically opposite pentagonal faces (1.22 nm), square faces (1.27 nm), and triangular faces (1.27 nm) of the third shell.This remarkable Pd 145 nanocluster, whose metal-core geometry was unambiguously characterized from complete crystallographic analyses of X-ray data for two crystals (from different preparations, crystals A and B), [1, 2] was isolated from the reduction of a monomeric square-planar palladium precursor, [Pd(PEt 3 ) 2 Cl 2 ]. [3, 4] The geometrical conformity of the 55 interior metal atoms within the third shell of 1 to the well-known two-shell icosahedral Mackay hard-sphere model [5] had not been previously observed in single-crystal X-ray crystallographic determinations. [6,7] The third-shell polyhedron in this unprecedented close-packed multi-shell metal carbonyl cluster possesses 60 equivalent vertices along with 12 pentagonal, 20 equilateral triangular, and 30 square faces; [8] this semi-regular (Archimedean) polyhedron, named rhombicosidodecahedron (with Schläfli symbol 3.4.5.4), [9] is a heretofore crystallographically unknown stereoisomer of the universally familiar C 60 buckyball, an icosahedrally truncated semi-regular polyhedron of I h symmetry with 60 equivalent vertices and 12 pentagonal and 20 hexagonal faces.Because the formation of 1 is extremely sensitive to reaction boundary conditions, extensive systematic preparative efforts have been made during the last 24 months to provide a reproducible but (as yet) low-yield synthesis. The Goddess Fortuna recently revisited our laboratory in that crystals of 1 were again isolated and its crystal structure redetermined. The fact that 1 has 55 interior Pd atoms makes it an ideal model for experimental operational tests of previous interpretations of size-dependent physical properties (attributed to quantum-size effects) reported [10] for several giant noncrystalline, (N,O)-ligated, full-shell palladium clusters (ideally formulated from other measurements as fiveshell Pd 561 species by the Moiseev and Schmid groups [11, 12] and as seven-/eight-shell Pd 1415 /Pd 205...

A Keplerian Ag90 nest of Platonic and Archimedean polyhedra in different symmetry groups

“…2e), where the numbers 5, 4, and 3 represent faces around that vertex, respectively, 5-gons, 4-gons, and 3-gons. Of note, the outer Ag 60 shell is geometrically reminiscent of the third shell (Pd 60 ) in Dahl's Pd 145 cluster 15 . All vertices on these three polyhedra are Ag(I) atoms, and all edges are built from the connection of adjacent two Ag atoms.…”

“…ncouraged by masterpieces of self-assembly in biology [1][2][3][4][5] , some seminal metal clusters 6 of nanometer size have been assembled from simple components [7][8][9][10][11][12] , such as Al 77 13 , Gd 140 14 , Pd 145 15 , Ag 374 16 , and Au 246 17 . Among families of metal clusters, silver nanoclusters benefit from the exceptional versatility of silver(I) atoms, which have flexible coordination preferences, a tendency to form argentophilic interactions and a susceptibility to reduction, all properties enriching the number of members and types of this family [18][19][20] .…”

Kupferchalkogenid‐Clusterverbindungen mit Brom‐funktionalisierter Ligandenhülle

“…[1] Beispielsweise finden sich darunter Arbeiten, in denen über eine Funktionalisierung von Metallnanopartikeln oder die Dimerisierung von Goldnanopartikeln mittels verbrückender Moleküle berichtet wird. [2] Obwohl es inzwischen schon viele Beispiele für die Synthese großer Cluster-Moleküle gibt, [3][4][5][6][7][8] wurde der Einfluss von funktionellen Gruppen in der Ligandenhülle solcher Cluster bislang wenig untersucht. Die meisten bisher publizierten Arbeiten beschäftigen sich mit Ligandenaustauschreaktionen.…”

Robustness of the chiral-icosahedral golden shell I-Au60 in multi-shell structures

“…In 2008, Chaki et al 19 demonstrated mass spectrometrically that the clusters comprised only 144 Au atoms (plus the 59-60 thiolate ligands), rather than the expected 145 count established previously for Pd 145 by Tran et al 18 This surprise prompted O. López-Acevedo et al 20 to verify by DFT-based optimization that the more stable version centered on a vacancy, i.e. its central I h -Au 12 cage is hollow, lacking a central atom, consistent with the reformulation Au 144 (SR) 60 .…”

“…First reports of a singular, 'ubiquitous', Au cluster of approximately ∼145-atoms (core mass ∼29-kDa) date to 1995-6. 17 Next, a primitive structure-model was tested, derived directly from the 'I h -Pd 145 structure' (hereafter denoted simply by 'Pd 145 structure') 18 that had been totally solved by 1999. (See brief description immediately below.)…”