Bimetallic Carbonyl Clusters Research Articles

Studies on reactivity of platinum-based heterobimetallic carbonyl clusters

The present article describes the synthesis and reactivity of platinum-based trinuclear carbonyl clusters L2PtRu2(CO)8 where L2 = 1,3-bis(diphenylphosphino)propane (dppp) and 1,2-bis(diphenylphosphino)ethane (dppe). Oxidative addition reactions of these bimetallic carbonyl clusters with methyl iodide yield products such as L2PtMeI and L2PtI2 and Ru3(CO)12. On heating with diphenylacetylene, L2PtRu2(CO)8 gives high yields of the corresponding products like L2PtRu2(CO)6(μ3-η2-PhC2Ph) (L = PPh3 or L2 = dppe or dppp). Hydrogenation of (dppe)PtRu2(CO)6(μ3-η2-PhC2Ph) yields stilbene and a new carbonyl cluster, [(dppe)2Pt2Ru(CO)4] possessing two platinum centers of the type {Pt2Ru}. All the products were isolated and characterized by FT-IR, NMR, and mass spectral analysis.

Structural Interconversion of Bimetallic Carbonyl Clusters ­Induced by a NHC Ligand and Its Selectivity on Fragments

AbstractThe reactions of IMes‐HCl with bimetallic iron‐copper clusters were investigated and it showed that interconversions among bimetallic FexCuy(CO)zn– clusters were induced by IMes‐HCl. The reaction priority of IMes‐HCl with fragments in FexCuy(CO)zn– was also investigated and the reaction behaviors of zero valent Fe(CO)4 and divalent Fe(CO)4 with IMes‐HCl were discussed.

Facile synthesis of platinum based heterobimetallic carbonyl clusters from bis(1-alkenyl)Pt(II) precursors

A new route for the high yield synthesis of platinum containing mixed bimetallic carbonyl clusters of the type [PtRu2(CO)8L2] (where L2=dppe, 1,2-bis(diphenylphosphino)ethane or dppp, 1,3-bis(diphenylphosphino)propane; L=PPh3) by the reaction of platinum-alkenyl [PtL2(1-alkenyl)2] precursors with [Ru3(CO)12] is reported. An unexpected multinuclear mixed cluster, [PtRu4(CO)13(μ4-PCH2CH2CH2PPh2)], obtained under prolonged refluxing conditions was also isolated. All the products were isolated and characterized by various spectroscopic and analytical techniques. In solution, the complex [PtRu2(CO)8(PPh3)2] gives [Pt2Ru(-CO)3(CO)2(PPh3)3] and Ru3(CO)11(PPh3). The structures and relative energies of the intermediates and transition states in the proposed reaction mechanism for the {PtRu2} clusters have been investigated using density functional theory.

Performance of novel bimetallic carbonyl clusters as PEM fuel cell anodes, a comparative study

This work describes the performance of novel bimetallic catalysts, prepared from ruthenium, rhodium and iridium carbonyl clusters by a thermolysis procedure in o-dichlorobenzene. The electrochemical characterization by the rotating disk electrode technique in 0.5 mol L−1 H2SO4 showed that the RuxIry(CO)n, RuxRhy(CO)n and RhxIry(CO)n clusters are able to perform both the hydrogen oxidation reaction (HOR) and oxygen reduction reaction (ORR), even in the presence of fuel cell contaminants such as CO and methanol, respectively. These promising results led us to evaluate the new materials as electrodes in a single fuel cell, using a Fuel Cell Test System designed and built in our group. The performance results of the three bimetallic clusters as anodes in a hydrogen PEM fuel cell are presented in this work. In the tests different H2 and O2 gas flows were fed into the cell to determine the most adequate ratio for maximum power. In the absence of CO, the results showed that although the three bimetallic materials had a similar performance to that of platinum with low flows of both reactants, RuxIry(CO)n showed the best electrocatalytic parameters. When the hydrogen fuel feed was contaminated with 100 ppm and 0.5% CO, the commercial platinum activity decreased considerably or was completely lost. However, while the current density of the novel materials also decreased in the presence of CO, it was significantly above that of platinum nanoparticles, the RhxIry(CO)n and RuxIry(CO)n catalysts showing the best performance in the presence of 100 ppm CO and 0.5% CO respectively. These results are promising in the context of PEM fuel cells using reforming hydrogen.

Gold/Iron Carbonyl Clusters for Tailored Au/FeOx Supported Catalysts

A novel preparation method was developed for the preparation of gold/iron oxide supported catalysts using the bimetallic carbonyl cluster salts [NEt4]4[Au4Fe4(CO)16] and [NEt4][AuFe4(CO)16] as precursors of highly dispersed nanoparticles over different supports. A series of catalysts with different metal loadings were prepared and tested in the complete oxidation of dichlorobenzene, toluene, methanol and in the preferential oxidation of CO in the presence of H2 (PROX) as model reactions. The characterization by BET, XRD, TEM, H2-TPR, ICP-AES and XPS point out the way the nature of the precursors and the thermal treatment conditions affected the dispersion of the active phase and their catalytic activity in the studied reactions.

Ruthenium and Iron Carbonyl Clusters Catalyzed Reduction of N,N-dimethylbenzamide and N,N-diethyl<i>-</i>(3-methyl)benzamide

One new Ruthenium and one known Iron bimetallic carbonyl clusters containing triphos (1,1,1-tris(diphenylphosphinomethyl)ethane) ligand have been prepared as catalyst to study the reduction of amide to amine. All clusters were characterized by elemental analysis, 1HNMR, 31PNMR and IR spectroscopy. The reduction of N,N-dimethylbenzamide and N,N-diethyl-(3-methyl) benzamide catalyzed by Ru and Fe carbonyl clusters were investigated at 100 ~ 110 °C for 24 ~ 28h, polymethylhydrogensiloxane (PMHS) as reduction agent. The products were analysized using GC-MS, IR and UV-vis spectroscopy and an excellent yield (97%) of N,N-diethyl- (3-methyl)benzamine was obtained when using 3 mol% of bimetallic ruthenium carbonyl cluster as catalyst. The data of IR and UV-vis show that the frameworks of clusters are not changed remarkably during the reaction.

Two-Dimensional Bimetallic Carbonyl Cluster Complexes with New Properties and Reactivities

The new electron-rich, anionic, planar cluster complex [IrRu(6)(CO)(23)](-), 5, isolated as a PPN salt, PPN = [Ph(3)PNPPh(3) ](+), has been synthesized and characterized crystallographically. The complex exhibits unusual absorption and emission properties. Computational analyses have been performed to explain its metal-metal bonding and electronic properties. Anion 5 reacts with [Ph(3)PAu][NO(3)] to yield the uncharged planar complex Ru(5)Ir(CO)(20)AuPPh(3), 6, by metal atom substitution.

Total oxidation of volatile organic compounds on Au/FeO x catalysts supported on mesoporous SBA-15 silica

A series of Au/FeO x /SBA-15 type materials were prepared by two methods: one conventional and one non-conventional: gold deposition-precipitation on FeO x /SBA-15 and bimetallic carbonyl cluster deposition on SBA-15, respectively. Both chemical physical characterization and catalytic activity tests in the complete combustion of methanol show that the new preparation method of Au/FeO x -supported catalysts leads to the anchoring of the Au by modifying the surface of SBA-15 with FeO x species. This effect results in a considerable improvement in catalyst performance as compared to the classic preparation by deposition-precipitation of Au on SBA-15 and FeOx/SBA-15.

Design of nano-sized FeO x and Au/FeO x catalysts supported on CeO 2 for total oxidation of VOC

The total oxidation of methanol and toluene, chosen as representative VOCs, was investigated over CeO 2-supported Au/FeO x catalysts prepared utilizing the bimetallic carbonyl cluster salt [NEt 4][AuFe 4(CO) 16]. Characterization data showed that the catalysts prepared by the reported method exhibit highly and homogeneously dispersed iron oxide species on the ceria support together with small gold nanoparticles, whose size increases on increasing the amount of gold/iron. Addition of iron oxide species did not substantially increase the methanol combustion activity of ceria, whereas the presence of the mixed gold and FeO x species has been found to strongly enhance the activity towards the total oxidation of methanol. In the case of the toluene combustion the addition of FeO x or FeO x /Au species caused a significant decrease in the activity of the bare CeO 2. The above catalytic behavior was rationalized on the basis of different interactions occurring among gold, iron oxide and cerium oxide, which synergically affects both the reactivity of the surface oxygen and the capacity of the support to adsorb the organic reactant.

Catalytic combustion of toluene over cluster-derived gold/iron catalysts

The total oxidation of toluene was investigated over TiO 2-supported gold/iron catalysts prepared utilizing the [NEt 4][AuFe 4(CO) 16] bimetallic carbonyl cluster salts. The catalysts have been characterized by means of infra-red spectroscopy (FT-IR), inductively coupled plasma spectrometry (ICP), X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), total specific surface area (BET), X-ray photoelectron spectroscopy (XPS) and temperature programmed reduction (TPR) analyses. The novel preparation method resulted in iron oxide species finely and homogeneously distributed on the TiO 2 and on small gold nanoparticles. The presence of gold has been found to enhance the selectivity of iron oxides towards the complete oxidation of toluene while the extent of the interaction between the two metals is important for catalytic activity.

Synthesis and Characterization of Magnetic Nanoalloys from Bimetallic Carbonyl Clusters

Magnetic nanoparticles are potentially useful for biomedical research because of their unique chemical and physical properties. In particular, magnetic alloy nanoparticles are of interest because o...

Gold/iron carbonyl clusters as precursors for TiO 2 supported catalysts

A series of supported gold/iron catalysts has been prepared from bimetallic carbonyl clusters and characterized to determine how the nature of the precursors and the thermal treatment conditions affected the dispersion of the active phase and the catalytic activity. The chemical–physical characterization, and the catalytic tests carried out, evidenced that the deposition of bimetallic Au/Fe carbonyl clusters on a titania support, and their following controlled decomposition, is a way to obtain stable catalysts, active in the decomposition of toluene.

Bimetallic Cluster Provides a Higher Activity Electrocatalyst for Methanol Oxidation

The cluster complex Pt2Ru4(CO)18 was used as a precursor to prepare a 60 wt% 1:2 Pt:Ru nanoparticles on carbon (PtRu/C) for use as an electrocatalyst for methanol oxidation. This bimetallic carbonyl cluster complex was found to provide smaller, more uniform bimetallic nanoparticle that exhibited higher electrocatalytic activity than a 60 wt% 1:1 Pt:Ru commercial catalyst from E-Tek. Using bimetallic cluster precursors simplifies the synthetic procedures by reducing the need for high temperature reduction and assures a more intimate mixing of the two different metals. Transmission electron microscopy (TEM) images of the catalyst obtained from the cluster precursor showed bimetallic nanoparticles having a narrow size range of 2–3 nm that were dispersed uniformly over the surface of the support. Images of the commercial catalyst showed particles 3–4 nm in diameter that tended to agglomerate near the edges of the carbon support particles. Cyclic voltammograms of methanol oxidation from the two catalysts showed significantly higher activity for the cluster-derived catalyst. The onset potential for methanol oxidation for the cluster-derived catalyst was approximately 170 mV lower than that of the commercial catalyst at 100 A/g Pt, and approximately 250 mV lower at 400 A/g Pt.

Intrazeolite anchoring of [HRuCo3(CO)9(μ2-CO)3]: Synthesis and reversible decarbonylation

The synthesis of intrazeolite anchoring of [HRuCo3(CO)9(μ2-CO)3] involves the adsorption of metal carbonyl species into zeolite cages followed by reductive carbonylation under a mixed CO and H2 atmosphere. The physicochemical characterization of the samples was based on a multianalytical approach, including Fourier transform-infrared, extended x-ray absorption fine structure spectroscopies, and CO/H2 gas chemisorption. The research encomassed several key points as follows: (a) The generation process of bimetallic carbonyl clusters was considered to occur through the interaction of [Ru–Co], Co(CO)4− and RuI carbonyls, and conversion into [HRuCo3(CO)9(μ3-CO)3] and further to [HRuCo3(CO)9(μ2-CO)3] isomer. (b) There is significant bimetallic interaction. (c) Internal and external confinement of [HRuCo3(CO)9(μ2-CO)3] were compared. (d) The intrazeolite anchoring of [RuCo3] carbonyl clusters shows a strong reaction with the extraframework Na+ α-cage cations, through involvement of the oxygen end of the bridging carbonyl ligands.

Intrazeolite Anchoring of Co, Ru, and [Ru−Co] Carbonyl Clusters: Synthesis, Characterization, and Their Catalysis for CO Hydrogenation

This paper focuses on the intrazeolite anchoring of Co, Ru, and Ru−Co carbonyl clusters and their catalytic performances for CO hydrogenation. The synthesis of intrazeolite anchoring of [HRuCo3(CO)9(μ2-CO)3] involves the adsorption of metal carbonyl species into zeolite cages followed by reductive carbonylation under a mixed CO and H2 atmosphere. The physicochemical characterization used a multianalytical approach, including FT-IR and EXAFS spectroscopies and CO/H2 gas chemisorption. The research concluded several key points as follows. (i) There is significant bimetallic interaction. (ii) The generation process of bimetallic carbonyl clusters was considered to occur through the interaction of [Ru−Co], Co(CO)4-, and RuI carbonyls, and conversion into [HRuCo3(CO)9(μ3-CO)3] and further to [HRuCo3(CO)9(μ2-CO)3] isomer. (iii) Internal and external confinement of [HRuCo3(CO)9(μ3-CO)3] were compared. (iv) The intrazeolite anchoring of [RuCo3] carbonyl clusters shows a strong reaction with the extraframework Na+ α-cage cations through involvement of the oxygen end of the bridging carbonyl ligands. (v) The bimetallic Ru−Co cluster catalyst shows higher CO conversion and oxygenates selectivity than the monometallic Co or Ru cluster. A high Co ratio in the Ru−Co cluster catalyst enhances the catalytic activity and the selectivity of oxygenates. (vi) The catalytic properities such as oxygenates selectivity depend on cluster size. Basic NaX is superion to NaY in enhancing oxygenates selectivity. (vii) Infrared spectra, 13CO, D2 isotopic exchange, and mass studies prove that a surface η2-formyl species adsorbed on Ru−Co interaction sites is an intermediate of oxygenate formation. The adjacent Ru−Co sites suppress η2-formyl adspecies dissociation and promote formyl species insertion into alkyl adspecies to enhance heavy oxygenate formation. (ix) The deactivated bimetallic Ru−Co cluster catalyst can be regenerated by hydrogen treatment, whereas the monometallic Co cluster catalyst cannot be regenerated.

Surface chemistry and catalysis of SiO 2-supported RhCo 3(CO) 12

The interaction of the RhCo 3 cluster with the SiO 2 surface has been investigated via decarbonylation of RhCo 3 (CO) 12 SiO 2 under different atmospheres by IR spectroscopy. The bimetallic RhCo 3 framework is intactly preserved on the surface after thermal treatments of RhCo 3 (CO) 12 SiO 2 at 623 K under vacuum, hydrogen and oxygen (or air), which is able to regenerate the initial bimetallic carbonyl cluster under a CO atmosphere. In contrast, the RhCo 3 SiO 2 sample without undergoing any thermal treatment is readily disintegrated by CO to result in Rh +(CO) 2 and Co 2+ with the aid of a concerted oxidation by surface OH −. IR study also shows that RhCo 3(CO) 12 is reversibly dissociated to Rh 6(CO) 16 and Co 2(CO) 8 on the surface by CO. In situ IR observations reveal that the equilibrium favoring the regeneration of RhCo 3(CO) 12 is established at 423 K under atmospheric hydroformylation pressure in terms of the interconversion between the bimetallic cluster and the monometallic clusters, and that RhCo 3 (CO) 12 SiO 2 is stable and responsible itself for the catalysis toward ethylene hydroformylation. Atmospheric catalytic results illustrate that RhCo 3 (CO) 12 SiO 2 has high activity and stability for the formation of propanal and n-propanol.

IR studies on the preservation of RhCo 3 clusters on the surface of SiO 2

The adsorption of RhCo 3(CO) 12 on the SiO 2 surface, and the interactions of SiO 2-supported RhCo 3(CO) 12 and SiO 2-supported RhCo 3(CO) 12-derived catalyst with CO have been studied at room temperature by IR spectroscopy. A strong physisorption of RhCo 3(CO) 12 on partially dehydroxylated SiO 2 occurs spontaneously, which results in a dramatic change of carbonyl spectral pattern and downward shifts of both linear and bridged carbonyl bands. The SiO 2-grafted RhCo 3(CO) 12 is characterized by two carbonyl bands at 2028 and 1830 cm −1. These observations may be interpreted in terms of a nucleophilic attack of surface oxygen containing groups on the cobalt atoms of the bimetallic cluster. Following decarbonylation of RhCo 3(CO) 12 SiO 2 under H 2 at 623 K, the resulting catalyst surface can be recarbonylated by to regenerate the starting bimetallic carbonyl cluster which is then gradually disintegrated to Rh 6(CO) 16 and Co 2(CO) 8 under CO. In parallel, the precursor RhCo 3(CO) 12 SiO 2 itself readily reacts with CO to dissociate to Rh 6(CO) 16 and Co 4(CO) 12. The reaction mixture is not only identified on the surface during exposure to CO but also extracted from the surface into the organic solvent. The results suggest that the RhCo 3 cluster framework is preserved on SiO 2 despite that the precursor has undergone the severe thermal decarbonylation treatment, and that RhCo 3(CO) 12 is regenerated by CO adsorption. A tight SiO 2 surface-bound RhCo 3 cluster is proposed for the supported bimetallic catalyst in terms of cluster-support interaction. In addition, the discrepancy between the regenerated supported RhCo 3(CO) 12 and the precursor during the dissociation processes is discussed.

Synthesis and Reversible Decarbonylation of Zeolite-Entrapped Bimetallic Carbonyl Clusters, [HCoRu3(CO)13

Molecular Co−Ru bimetallic carbonyl clusters, [HCoRu3(CO)13]/NaY, were synthesized by reductive carbonylation of Ru3(CO)12/NaY and Co2(CO)8 under CO/H2 atmosphere. The clusters and their reversible decarbonylation were characterized by infrared spectroscopy. The data confirm the presence of intermediates in the reversible formation of bimetallic carbonyl clusters. This provides further indication of the potential for zeolite cages as microreactors for chemical synthesis.

CO hydrogenation towards higher alcohols catalysed on SiO2-grafted and zeolite-entrapped Ru, Co and RuCo bimetallic clusters: Their EXAFS and FTIR characterization and catalytic performances

Some Ru and Co carbonyl clusters in zeolite pores such as Ru3(CO)12/NaY, [HRu6(CO)18]−/NaY, [Ru6(CO)18]2−/NaX, Co4(CO)12/NaY and Co6(CO)16/NaY were prepared by the ship-in-bottle technique, and characterized by FTIR and EXAFS. The RuCo bimetallic carbonyl cluster was prepared by reductive carbonylation of the oxidized RuCo/NaY, which provides the proposed assignment to [HRUCo3(CO)12]/NaY. The tailored Ru, RuCo and Co catalysts were prepared by H2 reduction from the precursors, e.g. Ru, RuCo bimetallic and Co carbonyl clusters impregnated on SiO2 and entrapped in NaY and NaX zeolites. The RuCo bimetallic carbonyl cluster-derived catalysts showed substantially higher activities and selectivities for oxygenates such as C1–C5 alcohols in CO hydrogenation (CO/H2 = 0.33-1.0, 5 bar, 519–543 K). By contrast, hydrocarbons such as methane were preferentially obtained on the catalysts prepared from Ru6, Ru3 and Co4 carbonyl clusters and provided lower CO conversion and poor selectivities for oxygenates. The RuCo bimetals are proposed to be associated with the selective formation of higher alcohols in CO hydrogenation.

Mixed-bimetal ruthenium carbonyl clusters supported on silica: Activity and selectivity in CO + H 2 conversion

The catalytic performance of bimetallic Ru-M (M = Co,Fe, Ni, Mo, Rh, Cr, Mn) catalysts prepared from a series of RuM carbonyl clusters in CO hydrogenation has been investigated. The catalysts derived from Ru-Co, Ru-Fe and Ru-Mo bimetallic carbonyl clusters showed high activity and selectivity for higher oxygenates, compared with the Ru6/ SiO2 catalyst prepared from impregnation of monometallic cluster Ru6C(CO)17. For Ru-Ni and Ru-Rh catalysts, they did not show high promotion for the formation of oxygenates although the selectivity was over 10% at 519 K. The promoters such as Mn and Cr in Ru-Mn and Ru-Cr catalysts intensively led to a decrease of oxygenate amount, in comparison with to Ru6/SiO2catalyst. In situ FT-IR studies revealed that the intensity of band at 1584 cm-1 for Ru-M (M=Co,Fe and Mo) bimetallic cluster-derived catalysts at 453 K under syngas (CO/H2= 0. 5) has a good linear relationship to rates of oxygenate formation, whereas the band at 1584 cm-1 was not observed for Ru-Mn, Ru-Cr, Ru-Rh and Ru-Ni bimetallic and monometallic cluster- derived catalysts showing poor activity for oxygenates. This strongly suggested that the band at 1584 cm-1 is likely related to an intermediate to produce oxygenates in CO hydrogenation. Isotopic adsorption of 13CO and D2as well as chemical trapping of surface intermediate suggested that the band at 1584 cm-1 corresponds to fornyl species.