Synthesis and characterization of a series of diphosphine ligated Pt-Au cluster compounds

Don A. Krogstad, Victor G. Young, Louis H. Pignolet

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Abstract

A series of diphosphine {Ph2P(CH2)nPPh2, n = 2-4, abbreviated P-n-P} ligated platinum-gold cluster compounds has been synthesized in high yield by ligand exchange reactions with PPh3 ligated, hydrido Pt-Au clusters. The exchange reaction between [(H)(PPh3)Pt(AuPPh3)7]2+ and the P-2-P and P-3-P ligands gives the clusters [(PPh3)PtAu8(P-n-P)4]2+ (1, 2), and with P-4-P the cluster [(P-4-P) PtAu6(P-4-P)3]2+ (3) is formed. The higher nuclearity cluster [PtAU10(P-3-P)5]2+ (8) was prepared by reaction of [(H)Pt(AuPPh3)9]2+ with P-3-P. All of these clusters have the 18-electron configuration and thus are unreactive with small electron donor molecules such as CO, Hg and H2. Clusters 2,3 and 8 react with the Lewis acids MX (MX = CuCl and AgNO3) giving tri-metallic compounds of higher nuclearity. The products of the MX addition to 1 and 2 are the four new clusters [(PPh3)Pt(MCl)Au8(P-n-P)4]2+ where n = 2 and 3 and M = Cu and Ag (4-7). The reaction of MX with 8 gives only the double addition products [Pt(MCl)2Au10(P-3-P)5]2+ (9, 10). The molecular structures of clusters 2, 3, 5, 7 and 8 were determined by single crystal X-ray diffraction (Mo Kα, λ = 0.71037 Å, 173 K; crystal data for 2: P1̄, a= 17.1484(4), b = 20.8146(5), c = 23.1098(5), α = 71.284(1) Å, β = 70.717(1), γ = 71.632(1)°, V = 7169.6(3) Å3, Z = 2, R = 0.10; 3: P1̄, a = 14.833(1), b = 15.905(2), c = 27.068(3) Å, α = 81.175(7), β = 77.088(12), γ = 67.742(6)°, V = 5743.7(10) Å3,Z = 2, R = 0.051; 5: P21/c, a = 24.353(3), b = 26.326(3), c = 20.554(2) Å, β = 108.082(6)°, V = 12526(2) Å3, Z = 4, R = 0.067; 7: P1̄, a = 17.4401(3), b = 18.4505(2), c = 23.1111(3) Å, α = 97.615(1), β = 104.731(1), γ = 104.275(1)°, V = 6817.3(2) Å3, Z = 2, R = 0.087; 8: P1̄, a = 16.048(3), b = 16.015(3), c = 30.790(5) Å, α = 83.408(12), β = 89.677(12), γ = 65.135(13)°, V = 7124(2) Å3 Z = 2, R = 0.096). All have Pt-centered, icosahedral fragment geometries for their PtMAu8 metal frames with the diphosphine ligands bridging adjacent Au atoms and also chelated to Pt in 3. The diphosphine ligated clusters are less labile and less fluxional than their PPh3 analogs due to constraints on the number of skeletal rearrangement pathways imposed by the bridging diphosphine ligands.

Original languageEnglish (US)
Pages (from-to)19-32
Number of pages14
JournalInorganica Chimica Acta
Volume264
Issue number1-2
DOIs
StatePublished - Nov 1 1997

Keywords

  • Cluster complexes
  • Crystal structures
  • Diphosphine complexes
  • Gold complexes
  • Heterometallic complexes
  • Platinum complexes

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