Leijun Hao

Models for bimetallic catalysts: selectivity in ligand addition as a function of rhenium oxidation state in Pt3Re clusters

The ligands CO, P(OR)3, and X–(X = Cl, Br, I) add selectively to the Re Pt3 sites in the coordinatively unsaturated clusters [Pt3{Re(CO)3}(µ-dppm)3]+ and [Pt3{ReO3}(µ-dppm)3]+ respectively, dppm = Ph2PCH2PPh2: the selectivity thus displays a remarkable dependency on the oxidation state of rhenium.

The bicluster oxidative addition as a route to bicapped hexaplatinum clusters

Abstract The reaction of either the 84-electron cluster [Pt 6 (μ-CO) 6 (μ-dppm) 3 ] ( 1 ) or the 82-electron cluster [Pt 6 (CO) 6 (μ-dppm) 3 ] 2+ ( 2 ), dppm = Ph 2 PCH 2 PPh 2 , with SnX 3 − or Hg 2 X 2 gave the corresponding bicapped trigonal prismatic 86-electron clusters [Pt 6 ( μ 3 -SnX 3 ) 2 ( μ -CO) 6 ( μ -dppm) 3 ] ( 3 : X = F( 3a , Cl( 3b ), Br( 3e ) or [ Pt 6 (μ 3 - HgX ) 2 (μ- CO ) 6 (μ- dppm ) 3 ] 4 : X = Cl ( 4a ) , Br ( 4b ), l ( 4c ), respectively. The new clusters 3 and 4 have been characterized spectroscopically and 4c has also been characterized by X-ray diffraction. Crystals of 4c·CH 2 Cl 2 ·2Et 2 O are monoclinic, space group P 2 1 c , a=20.092(9), b=18.718(7), c=26.258(7) A , β=108.09(3)° V=9387(6) A 3 , Z =4. The molecular core in 4c is a Pt 6 trigonal prism with each triangular Pt 3 face capped by an Hgl fragment. The intertriangle PtPt bond distances (2.910(1)–2.948(1) A) are longer than the intratriangle PtPt distances (2.634(1)–2.687(1) A) and this is consistent with EHMO calculations. The reaction of 1 with Hg 2 X 2 to give 4 is termed a bicluster oxidative addition; according to predictions from EHMO calculations it should lead to stronger intertriangle PtPt bonding in 3 and 4 than in the precursor cluster 1 , but this is not suppored by structural data observed in 3c and 4c .

Tetrahedral platinum carbonyl clusters

The first carbonylplatinum clusters established crystallographically to have tetrahedral Pt4 cores are [Pt4H(CO)(µ- CO)3L4]ReO42 and [Pt4(µ-CO)2L4(ReO4)2]3, L = P(C6H11)3, having 56 and 54 cluster valence electrons (CVE), respectively.

Clusters as models for surface catalysis: a model for sulfide effects on Pt–Re catalysts

By reaction with propene sulfide, one or two sulfur atoms are added to the tetrahedral cluster cation [Pt3{Re(CO)3}(µ-dppm)3]+1(dppm = Ph2PCH2PPh2), to give [Pt3{Re(CO)3}Sn(µ-dppm)3]+(n= 1, 2; n= 2, 3); the reactions provide an interesting model for sulfidation of heterogeneous Pt–Re catalysts.