Tetyana Khimyak

Single-Step, Highly Active, and Highly Selective Nanoparticle Catalysts for the Hydrogenation of Key Organic Compounds

Pores for cluster catalysts: Nanoparticles of both Ru5Pt and Ru10Pt2, uniformly distributed along the inner walls of mesoporous silica, exhibit high catalytic performance in the single-step hydrogenation of dimethyl terephthalate (DMT, to 1,4-cyclohexanedimethanol (CHDM); see scheme), of benzoic acid (to cyclohexane carboxylic acid), and of naphthalene (in the presence of sulfur) to cisdecalin.

Bimetallic nanocatalysts for the conversion of muconic acid to adipic acidElectronic supplementary information (ESI) available: experimental details, EXAFS fit and refined EXAFS parameters. See http://www.rsc.org/suppdata/cc/b3/b300203a/

Adipic acid (2) production currently entails use and generation of environmentally harmful materials: an efficient catalyst, consisting of nanoparticles of Ru10Pt2 anchored within the pores of mesoporous silica, facilitates the production of (2) by hydrogenating muconic acid, that may be derived biocatalytically from D-glucose.

Preparation and characterization of bimetallic catalysts supported on mesoporous silica films

Thin (300-1000 nm) mesoporous silica coatings with hexagonal and cubic mesostructure have been prepared on Pyrex@ 7740 borosilicate glass substrates by the evaporation induced self assembly assisted sol-gel route. Prior to the synthesis, a 50 nm TiO 2 layer has been deposited on the substate by atomic layer deposition from titanium tetrachloride and water to reach better adhesion of coatings to the walls of the substrate. The coatings were produced by templating a silica precursor (TEOS) with an EO x PO y EO x amphiphilic triblock copolymer (EO = ethylene oxide, PO = propylene oxide, x = 106, y = 70) at a pH of 2. A surfactant/silica ratio of 0.0076 was found to be optimal at a spinning rate of 1500 rpm to obtain the coatings with a surface area above 500 m 2 /g and a monomodal pore size distribution with a mean pore size of 6.9 nm. Mixed-metal precursor clusters [Ph 4 P] 2 [Ru 5 PtC(CO) 15 ] have been inserted into the mesoporous support. Then, the mesoporo-encapsulated clusters were activated by gentle heating in vacuo at 200°C. The average diameter of the resulting, well-dispersed, isolated and anchored bimetallic nanoparticles is 1.4 nm. By this approach, the functionality of the relatively fragile metallic clusters is mediated through the rigid inorganic framework providing protection and the 3D distribution of the catalytic function. The resulting coatings can be used in a number of fine chemicals synthesis reactions.

The synthesis and characterisation of the cluster dianion [PtRu5C(CO)15]2- and its reactions with Au and Pt cationic fragments produced in situ

The neutral mixed-metal cluster [PtRu5C(CO)16] was reduced by KOH in methanol to give [Ph4P]2[PtRu5C(CO)15] 1 in 84% yield. Reaction of 1 with Au(PPh3)Cl afforded the gold derivative [PtRu5C(CO)15(AuPPh3)2] 2. Other reactions of 1 with [Pt(COD)Cl2] and [Pt(CO)(PPh3)Cl2] in the presence of silica yielded the new mixed-metal cluster compounds [Pt2Ru4C(CO)13(COD)] 3, [Ph4P]2[Pt3Ru10C2(CO)32] 4, [Pt4Ru5C(CO)16(PPh3)3] 5, [PtRu4C(CO)13(PPh3)] 6 and [Pt2Ru4C(CO)14(PPh3)] 7. Compounds 1–7 were characterised spectroscopically and the molecular and crystal structures of compound 1–5 were determined by single crystal X-ray crystallography.

Ligand substitutions in Ru–Pt clusters: isolation of compounds with unusual geometries

Ligand substitution reactions of the COD (1,5-cyclooctadiene) ligand for CO or phosphines in the clusters [Ru5C(CO)14Pt(COD)] (1) and [Ru6C(CO)16Pt(COD)] (2) were investigated. Reactions with carbon monoxide gave selectively [Ru5CPt(CO)16] (3) from 1, but led to loss of either a ruthenium or the Pt(COD) unit from the Ru6Pt cluster (2). Substitution of the COD ligand by PPh3 in 1 gave [Ru5C(CO)14Pt(PPh3)2] (8) selectively, while with dppm the main product of the reaction was [Ru5C(CO)14Pt(μ-dppm)] (10). On the other hand, the reactions involving [Ru6C(CO)16Pt(COD)] (2) and phosphines led mainly to extrusion of the Pt(COD) fragment and formation of Ru-only derivatives. More precisely, with triphenylphosphine, the two clusters [Ru6C(CO)16PPh3] (16) and [Ru6C(CO)15(PPh3)2] (18) were obtained from 2, while with dppm, the compounds [Ru6C(CO)15(dppm)] (15) and [Ru6C(CO)13(dppm)2] (19) were formed. In the latter case, two additional products of increased nuclearity were isolated: [Ru6C(CO)15Pt2(dppm)] (20) and [Ru6C(CO)16Pt3(dppm)2] (21). All the compounds described were characterised by spectroscopic methods and the structures of the new species were determined by X-ray crystallography.

High yield synthesis of Ru–Pt mixed-metal cluster compounds

The reaction of [PPN]2[Ru5C(CO)14] 1 or [PPN]2[Ru6C(CO)16] 2 [PPN+ = (PPh3)2N+] with Pt(II) compounds of general formula [PtX2Cl2] [X2 = (COD), (PPh3)2 and (PPh3)(CO)] (COD= 1,5-cyclooctadiene) have been investigated and the products of simple or double addition, viz. [Ru5PtC(CO)14(COD)] 3, [Ru5PtC(CO)14(PPh3)2] 4, [Ru5PtC(CO)15(PPh3)] 5, [Ru5Pt2C(CO)15(PPh3)2] 6, [Ru6PtC(CO)16(COD)] 7, [Ru6Pt2C(CO)15(COD)2] 8, obtained. The molecular and crystal structures of 3-8 have been established by single crystal X-ray analysis. Compounds 3-7 all contain an intact Ru core with Pt fragment(s) capping triangular or square faces. The resulting mixed-metal core is octahedral for the clusters Ru5Pt and face-capped octahedral for the clusters RunPtm (n = 5 or 6; m = 2 or 1). Only compound 8 did not follow this pattern, with the Pt fragments bridging two Ru-Ru edges of the otherwise unaltered Ru6C core.

Synthesis of Ru-M cluster compounds and their use as precursors for nanoparticle catalysts supported on mesoporous silica

Abstract Mixed-metal cluster compounds were used as precursors for the preparation of highly efficient supported nanoparticle catalysts.