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de Silva N, Dahl LF: Synthesis and structural analysis of the first nanosized platinum-gold carbonyl/phosphine cluster, Pt13 [Au2 (PPh3) 2] 2 (CO) 10 (PPh3) 4, containing a Pt-centered [Ph3PAu-AuPPh3]-capped icosahedral Pt12 cage. Inorg Chem. 2005 Dec 26;44(26):9604-6.
The preparation and molecular structure of the initial nanosized platinum-gold carbonyl cluster, Pt (13)[Au (2)(PPh (3))(2)](2)(CO)(10)(PPh (3))(4) (1), are described. A comparative analysis reveals its pseudo-D (2)(h) geometry, consisting of a centered Pt (13) icosahedron encapsulated by two centrosymmetrically related bidentate [Ph (3) PAu-AuPPh (3)]-capped ligands along with 4 PR (3) and 10 CO ligands, to be remarkably similar to that of the previously reported Pt (17)(mu (2)-CO)(4)(CO)(8)(PEt (3))(8) (2). Reformulation of 2 as Pt (13)[(PtPEt (3))(2)(mu (2)-CO)](2)(CO)(10)(PEt (3))(4) emphasizes the steric/electronic resemblance of the bulky-sized bidentate [Ph (3) PAu-AuPPh (3)] and [(PtPEt (3))(2)(mu (2)-CO)] capping ligands in 1 and 2, respectively, as well as their identical electron counts of 162 cluster valence electrons for a centered Pt (13) icosahedron. We hypothesize that analogous steric effects of their ligand polyhedra in 1 and 2 play a crucial role along with electronic effects in the formation and stabilization of these two nanosized clusters that contain an otherwise unknown centered icosahedron of platinum atoms. |
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