Synthesis and structure of a neutral trimetallic biicosahedral cluster, (Ph3P)(10)Au11Ag12Pt2Cl7. A comparative study of molecular and crystal structures of vertex-sharing biicosahedral mixed-metal nanoclusters

The synthesis and structure of a new, neutral Au-Ag-Pt vertex-sharing biico sahedral cluster, [(Ph3P)(10)Au11Ag12Pt2Cl7] (3), is reported. The title cl uster M was synthesized via a nea synthetic strategy based on preformed clu sters. The title cluster crystallizes in a monoclinic unit cell of P2(1)/m space-group symmetry with lattice parameters a = 16.553(14) Angstrom, b = 2 5.130(7) Angstrom, c = 29.633(13) Angstrom. beta = 103.03(5); V = 12009.3 A ngstrom (3) and Z = 2. The structure was refined to R-1 = 7.7% and R-2 = 9. 2% for 3585 independent reflections (20 less than or equal to 42 degrees) w ith I > 3 sigma. The metal core of the title structure call be described as two Pt-centered Au6Ag6 icosahedra sharing a common Au atom. The four metal pentagons adopt the staggered eclipsed-staggered (ses) configuration, or, the R(0) rotamer. The ten triphenylphosphine: ligands coordinate to the ten peripheral (surface) Au atoms in a radial fashion. There are five doubly-b ridging chloride ligands connecting two Ag, pentagons and two more chloride ligands coordinating terminally to two apical Ag atoms. The title cluster completes the series of Au-shared biicosahedral clusters with 0, 1, and 2 P t atom(s) occupying the two icosahedral centers, as exemplified by [(p-Tol( 3)P)(10)Au13Ag12Cl7](2+) (1), [(Ph3P)(10)Au-12 Ag12PtCl7](+) (2), and the t itle cluster [(Ph3P)(10)Au11Ag12Pt2Cl7] (3) respectively. The structure of the title cluster satisfies the site preference rules established for mixed -metal vertex-sharing polyicosahedral nanoclusters. The molecular structura l invariance and the ubiquity of the P2(1)/m space group for the crystal st ructures of the biicosahedral cluster series with Ph3P as phosphine ligands and conforming to the R(0) rotameric metal configuration are discussed. Fu rthermore, endo- and exo-icosahedral chemistries, and rotamerism and roulet tamerism of an extensive series of vertex-sharing biicosahedral nanocluster s, as well as their bonding implications. are described via, a comparative study.