Synthesis and Structural Analysis of the First Nanosized Platinum-Gold Carbonyl/Phosphine Cluster,Pt_(13)[Au_2(PPh_3)_2]_2(CO)_(10)(PPh_3)_4,Containing a Pt-Centered [Ph_3PAu-AuPPh_3]-Capped Icosahedral Pt_(12) Cage

摘要

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_(2h) geometry,consisting of a centered Pt_(13) icosahedron encapsulated by two centrosymmetrically related bidentate [Ph_3PAu-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_3PAu-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.