High-nuclearity palladium carbonyl trimethylphosphine clusters containing unprecedented face-condensed icosahedral-based transition-metal core geometries: proposed growth patterns from a centered Pd13 icosahedron†

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

“…Two and three face-fused centred icosahedra of Pd 23 and Pd 33 were found in Pd 39 (CO) 23 (PMe 3 ) 16 (Tran et al 2001) and Pd 69 (CO) 36 (PEt 3 ) 18 (Tran & Dahl 2003), respectively. The former cluster, which is completed by condensation of 16 Pd atoms on its centred face-fused Pd 23 biicosahedron, possesses an encapsulated trigonal bipyramidal Pd 5 fragment, which is deformed from pseudo-D 3h to a bent pseudo-C 2v geometry ( figure 19).…”

“…This latter Au 2 Pd 21 cluster exhibits a CV consisting of two reversible one-electron reductions (E 1/2 = −1.19 and −1.42 V) and two reversible one-electron oxidations (E 1/2 = −0.05 and 0.28 V). Therefore, the total electron capacity of the isostructural 23-atom Pd 23 or Au 2 Pd 21 clusters possessing a capped n 2 -octahedral geometry changes over a range of six electrons from 288 for [Pd 23 (CO) 16 in THF showed no reductions out to −2.8 V and no oxidations out to +1.0 V (Tran et al 2001).…”

“…The pseudo-T d Pd 16 Ni 4 core is composed of a n 3 tetrahedron with Ni atoms at the four vertices ( figure 12). The pseudo-D 3h Pd 33 Ni 9 core can be envisioned as a five-layer structure of three alternating centred 10-atom Pd 7 Ni 3 n 3 triangles (with Ni atoms at corner positions) and two six-atom n 2 Pd 6 triangles as follows: a(Pd 7 found in the C 3 symmetry cluster Pd 16 (CO) 13 (PR 3 ) 9 with R=Me (Tran et al 2001), Et (Mednikov et al 1991), both augmented with three wingtip Pd atoms (figure 17) and in the heterometallic [Au 2 Pd 14 (CO) 9 (PMe 3 ) 11 ] 2+ , containing a Pdcentred icosahedron, Au 2 Pd 11 , with an edge-condensed Pd 5 trigonal bipyramid (Copley et al 1995) (Tran et al 2001). In all three structures, a Pd-Pd bond between two interior atoms in each DI is also the edge of the encapsulated fragment that gives rise to a Pd 3 triangle in Pd 37 , a Pd 4 tetrahedron in Pd 29 Ni 3 and a Pd 5 trigonal bipyramid in Pd 35 .…”

“…Complementary pathways involve generation of reactive 'naked' (highly coordinatively unsaturated) [Pd] species in situ (equations (2.7) and (2.8)) that, (Tran et al 1998(Tran et al , 2001 (Wittayakun 2000).…”

Quantum chemical treatments of metal clusters

“…We now turn to the ligand-stabilized clusters of Tran et al (2000Tran et al ( , 2001. First of all, the metal cores found there are less stable than the other clusters of the same size and the proposed pathways for syntheses are likewise high in energy.…”