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

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.