Investigation of rhodium complexes in micro- and mesoporous materials by computer modeling, FTIR, and 31P MAS NMR

Tetracarbonyldichlororhodium(I) [Rh(CO)₂(μ -Cl)]₂ entrapped in faujasite type zeolites reacted with phosphines PMe_{3- x}Ph_x at 393-463 K to a different extent. Although according to computational studies phosphines with x<2 should be small enough to enter the micropore system, the reaction was in no case complete and led to a mixture of products as observed by IR spectroscopy. Furthermore surface-bonded rhodium carbonyl complexes were synthesized in mesoporous aluminium-containing MCM-41 material by reacting acetylacetonatodicarbonylrhodium(I) [Rh(acac)(CO)₂] with Brønsted-acidic centers under formation of a chemically bonded [Rh(CO)₂]- species and acetylacetone according to IR spectroscopy. The corresponding surface-bonded phosphine complex [(O_s)_x-Rh(chiraphos)] was synthesized and identified with IR and ³¹P MAS NMR spectroscopy.     

Homogeneous hydrogenation of dienes with rhodium complexes

Different Rh complex catalysts were compared for the hydrogenation of methyl sorbate and linoleate in the absence of solvents. At 100 C and 1 atm H₂ the following complexes, RhCl(Ph₃ P)₃ (Ph= phenyl), [RhClNBD]₂ (NBD=norbornadiene) and RhH(CO)(Ph₃P)₃, produced mainly methyltrans-2-hexenoate (34 to 56%). Their diene selectivity was not particularly high as they produced 14 to 41% methyl hexanoate. With RhCl(Ph₃ P)₃ constant ratios between rates of methyl sorbate disappearance and formation of methyltrans-2- andtrans-3-hexenoate indicate approximately the same activation energy for 1,2-addition of H₂ on the Δ4 double bond of methyl sorbate and for 1,4-addition to this substrate. In the hydrogenation of methyl linoleate with RhCl(Ph₃ P)₃, the kinetic curves were simulated by a scheme in which 1,2-reduction was more than twice as important as 1,4-addition of H₂ via conjugated diene intermediates. Although the complexes RhCl(CO)(Ph₃ P)₃ and [Rh(NBD)(diphos)]⁺PF₆ (diphos=diphosphine) were inactive in the hydrogenation of methyl sorbate, they catalyzed the hydrogenation of methyl linoleate at 100 C and 1 atm. Catalyst inhibition apparently was caused by stronger complex formation with methyl sorbate than with the conjugated dienes formed from methyl linoleate.     

SiO2‐supported bimetallic Rh–Co catalysts derived from [Rh(CO)2Cl]2 and cobalt carbonyls

According to the results of IR characterization and catalytic study in ethylene hydroformylation, bimetallic Rh–Co catalysts can be efficiently prepared from [Rh(CO)₂Cl]₂ and cobalt carbonyls by co‐impregnation on SiO₂. The reaction of Co₂(CO)₈ with [Rh(CO)₂Cl]₂ (Rh : Co = 1 : 3 atomic ratio) gives rapidly RhCo₃(CO)₁₂ on the surface of SiO₂. Although Co₄(CO)₁₂ is not reactive with [Rh(CO)₂Cl]₂ on SiO₂ to form directly RhCo₃(CO)₁₂, an equivalent bimetallic catalyst can be easily obtained from ([Rh(CO)₂Cl]₂ + Co₄(CO)₁₂)/SiO₂ or its derivative (Rh⁺ + Co²⁺)/SiO₂ (Rh : Co = 1 : 3 atomic ratio) under reducing conditions. This revised version was published online in July 2006 with corrections to the Cover Date.     

The new organometallic rhodium–iron homogeneous catalytic system for hydroformylation

The addition of Fe(CO)₅ to the systems with [Rh(acac)(CO)L] complexes (L = PPh₃, P(OPh)₃, P(NC₄H₄)₃) as catalyst precursors caused the increase of aldehydes yield in 1-hexene hydroformylation reaction (80°C, 10 atm) up to 71%. The IR and ¹H NMR measurements confirm the formation of an unstable bimetallic intermediate, [(H)(PPh₃)₃Rh(μ-CO)₂Fe(CO)₄], characterized with ν_CO at 1749 cm⁻¹ and hydrido signal at δ ™15.8 ppm. This revised version was published online in August 2006 with corrections to the Cover Date.     

A highly active bimetallic supported Rh–Co hydroformylation catalyst prepared from RhCl3 and Co2(CO)8

The preparation of a highly active bimetallic SiO₂‐supported Rh–Co catalyst from RhCl₃ and Co₂(CO)₈ (Rh:Co= 1 : 3 atomic ratio) has been studied by IR spectroscopy and ethylene hydroformylation, etc. Two steps are involved in the preparative process: (1) surface‐mediated synthesis of Rh⁺(CO)₂/SiO₂ from calcined RhCl₃/SiO₂; (2) impregnation of Rh⁺(CO)₂/SiO₂ with a Co₂(CO)₈ solution followed by H₂ reduction at 623 K. The IR results of reductive carbonylation of calcined RhCl₃/SiO₂ have been compared to those of uncalcined RhCl₃/SiO₂ at 373 K. In situ IR observations, extraction results and elemental analysis suggest that approximately 50% of RhCl₃ are transformed to Rh₂O₃ on the SiO₂ surface and that calcined RhCl₃/SiO₂ is converted to a mixture of [Rh(CO)₂Cl]₂ and [Rh(CO)₂O₂ (O_s: surface oxygen) under CO at 373 K. When this SiO₂‐supported mixture was submitted to impregnation with a Co₂(CO)₈ solution at room temperature, IR study and elemental analysis show that [Rh(CO)₂Cl]₂ reacts easily with Co₂(CO)₈ on the surface to give RhCo₃(CO)₁₂, whereas [Rh(CO)₂O₂ does not react with Co₂(CO)₈. Catalytic study in steady‐state ethylene hydroformylation shows that a catalyst thus derived is more active than a catalyst derived from RhCo₃(CO)₁₂/SiO₂ and a catalyst derived by coimpregnation of [Rh(CO)₂Cl]₂ and Co₂(CO)₈ on SiO₂. This result suggests that the high rhodium dispersion of [Rh(CO)₂O₂ plays a crucial role in the formation of highly dispersed bimetallic Rh–Co sites. This revised version was published online in July 2006 with corrections to the Cover Date.     

FTIR study of the rearrangement of adsorbed CO species on Al2O3-supported rhodium catalysts

The adsorption of CO at low temperatures (130–293 K) has been investigated on Rh/Al₂O₃ catalysts of low (0.001–1 wt%) Rh loadings by means of Fourier transform infrared spectroscopy. The surface structure of Rh produced at different reduction temperatures (573 and 1173 K) was shock-cooled to 130 K, where the addition of CO caused the appearance of the band due to bridge-bonded CO ((Rh⁰)₂–CO) on all samples. The appearance of the bands due to gem-dicarbonyl (Rh⁺(CO)₂) and linearly bonded CO (Rh_x–CO) depended on the Rh content and the reduction temperature of the catalysts. The positions and the integrated absorbances of the symmetric and asymmetric stretchings of the Rh⁺(CO)₂ changed with temperature. On the basis of the above findings the rearrangement of the adsorbed CO species (indirectly that of surface Rh) is discussed. This revised version was published online in July 2006 with corrections to the Cover Date.     

On the kinetics of CO oxidation by O2 over RhI(CO)2 catalytic species anchored to a zeolitic support

The reactivity of Rh^I(CO)₂ towards CO oxidation was studied on a model Rh(0.7 wt%)/HY material. The kinetic results show that Rh^I(CO)₂ exhibit a fairly low activity. It is therefore suggested that the catalytic species responsible for the enhanced activity of Rh/Ce_0.68Zr_0.32O₂ [Manuel et al., J. Catal. 224 (2004) 269] would rather be electron-deficient Rh clusters (Rh _n ^δ+ ).     

Electrochemical promotion of CO<Subscript>2</Subscript> hydrogenation on Rh/YSZ electrodes

The electrochemical promotion of the CO₂ hydrogenation reaction on porous Rh catalyst–electrodes deposited on Y₂O₃-stabilized-ZrO₂ (or YSZ), an O²⁻ conductor, was investigated under atmospheric total pressure and at temperatures 346–477 °C, combined with kinetic measurements in the temperature range 328–391 °C. Under these conditions CO₂ was transformed to CH₄ and CO. The CH₄ formation rate increased by up to 2.7 times with increasing Rh catalyst potential (electrophobic behavior) while the CO formation rate was increased by up to 1.7 times with decreasing catalyst potential (electrophilic behavior). The observed rate changes were non-faradaic, exceeding the corresponding pumping rate of oxygen ions by up to approximately 210 and 125 times for the CH₄ and CO formation reactions, respectively. The observed electrochemical promotion behavior is attributed to the induced, with increasing catalyst potential, preferential formation on the Rh surface of electron donor hydrogenated carbonylic species leading to formation of CH₄ and to the decreasing coverage of more electron acceptor carbonylic species resulting in CO formation.     

Preparation of Rh-containing polycarbonate films and the study of their chemical properties in the polymer

RhCl[P(C₆H₅)₃]₃ complexes have been incorporated in polycarbonate (PC) as a dispersion medium using cosolvent (THF). The interactions between Rh(I) complexes and polycarbonate polymer molecules are studied by infrared spectroscopy and thermal analysis. The reaction chemistry of Rh in PC films has been investigated by reacting Rh sites in PC with small gaseous molecules like CO, H₂, D₂, O₂, NO, C₂H₂, and C₂H₄ in the temperature range 25∼150°C. Various Rh–carbonyls, –hydride, –nitrosyl, and –superoxo dioxygen species formed in PC films are characterized by infrared spectroscopy. The Rh complexes in PC are easily reduced by reacting them with H₂ gas and such reduction results in the formation of small Rh metal particles of 20∼30 Å in diameter in PC. The Rh complexes in PC show interesting catalytic reactivities such as hydrogenation of olefin and acetylene, oxidation of CO, reduction of NO, methanol synthesis from CO or CO_2, and oxidation of alcohol under relatively mild conditions.     

Catalytic Reduction of 4-Nitrobenzoic Acid by cis-[Rh(CO)2(Amine)2](PF6) Complexes Under Water–Gas Shift Reaction Conditions: Kinetics Study

Rhodium(I) complexes of the type, cis-[Rh(CO)₂(amine)₂](PF₆) where (amine = 3-picoline, 2-picoline, pyridine, 2,6-lutidina or 3,5-lutidine) dissolved in 80% aqueous amine solutions catalyzed the selective reduction of 4-nitrobenzoic acid to 4-aminobenzoic acid under CO atmosphere. The importance of these catalytic systems is their high chemo selectivity for the aromatic nitro group of the 4-nitrobenzoic acid with respect to the carboxylic group, allowing the production of the desired aromatic amine in high yields. The 4-aminobenzoic acid production depends on the nature of the coordinated amine. The Rh/3,5-lutidine system, the most active catalyst among tested, displays turnover frequencies for 4-aminobenzoic acid production of about 173 moles per mole Rh per day for [Rh] = 1 × 10^?4 mol, [4-nitrobenzoic acid] = 3.82 × 10^?3mol, 10 mL of 80% aqueous 3,5-lutidine, P(CO) = 0.9 atm at 100 °C. Analyses of kinetic results for the Rh/3,5-lutidine system show a first order dependence on 4-nitrobenzoic acid concentration, a non-linear dependence on CO pressure, a segmented Arrhenius plot and dependence on the nature of the reducing gas agent. These data are discussed in terms of a possible mechanism.     

H/D Exchange on Silica-Grafted Tantalum(V) Imido Amido [(≡SiO)<Subscript>2</Subscript>Ta<Superscript>(V)</Superscript>(NH)(NH<Subscript>2</Subscript>)] Synthesized from Either Ammonia or Dinitrogen: IR and DFT Evidence for Heterolytic Splitting of D<Subscript>2</Subscript>

The silica-grafted Ta^(V) imido amido complex [(≡SiO)₂Ta(NH)(NH₂)], 2, obtained from the reaction of either ammonia or dinitrogen plus hydrogen with the silica-grafted hydrides [(≡SiO)₂Ta^(III)H], 1a, and [(≡SiO)₂Ta^(V)H₃], 1b, undergoes H/D exchange with D₂. In situ IR spectroscopy shows that the fully labelled compound [(≡SiO)₂Ta(ND)(ND₂)], 2-d, can be obtained by moderate heating (60 °C, 3 h) under D₂ atmosphere (550 torr, 300 eq. with respect to Ta), and that the exchange is reversible. The observed stretching and bending frequencies of 2-d are in agreement with the expected isotopic shift upon H/D replacement with respect to literature values reported for 2 and have been corroborated by the independent synthesis of 2-d by reaction of deuterated 1a and 1b with N₂ and D₂. Density functional theory (DFT) calculations, performed using a periodic or a cluster model, explored the structures and energetics of all minima involved in the reaction with H₂ and showed that among the explored pathways the energetically preferred mechanisms for H₂ reaction with [{(μ-O)[(HO)₂SiO]₂}Ta^(V)(NH)(NH₂)], 2q, is the heterolytic cleavage of either the imido Ta=N or the amido Ta-N bonds, to yield respectively [{(μ-O)[(HO)₂SiO]₂}TaH(NH₂)₂], 3q (ΔE = −9.5 kcal mol⁻¹ and ΔG_298K = +2.6 kcal mol⁻¹ with respect to 2q) and [{(μ-O)[(HO)₂SiO]₂}Ta(NH)(NH₃)], 4q (ΔE = −6.0 kcal mol⁻¹ and ΔG_298K = +7.9 kcal mol⁻¹ with respect to 2q). All activation barriers are moderate (between 17.7 and 30.2 kcal mol⁻¹) in agreement with the observed mild heating conditions necessary for the reaction to occur.     

High‐resolution imaging of nanoparticle bimetallic catalysts supported on mesoporous silica

Although conventional high‐resolution transmission electron microscopy is a powerful method for the elucidation of the structure of mesoporous solids (diameter of pores from 1.5 to 20 nm), it is far less capable than high‐resolution scanning transmission electron microscopy in identifying the spatial distribution of nanocrystals of catalysts encapsulated within the mesopores. Using high‐angle annular dark‐field imaging (either in a 100 or 300 keV STEM system), it is possible to locate precisely individual bimetallic nanoparticles (Ag₃Ru₁₀, Cu₄Ru₁₂ and Pd₆Ru₆ hydrogenation catalysts) supported on mesoporous silica, to determine their size distribution, and to record their characteristic X‐ray emission maps. It is also established that there is little tendency for elemental fragmentation of the bimetallic catalysts, all of which were prepared by decarbonylating, by thermolysis, precursor cluster carbonylate anions: [Ag₃Ru₁₀C₂(CO)₂₈Cl]⁻, [Ru₆C(CO)₁₆Cu₂Cl]²⁻ and [Ru₆Pd₆(CO)₂₄]²⁻. This revised version was published online in July 2006 with corrections to the Cover Date.     

Alkyne Metatheses in Transition Metal Coordination Spheres: Convenient Tungsten‐ and Molybdenum‐Catalyzed Syntheses of Novel Metallamacrocycles

Reactions of (CO)₅Re(Br), (η⁵‐C₅H₅)Ru(Cl)(PPh₃)₂, and [Pt(μ‐Cl)(C₆F₅)(S(CH₂CH₂‐)₂)]₂ with the alkyne‐containing phosphine Ph₂P(CH₂)₆C≡CCH₃ give the bis(phosphine) complexes fac‐(CO)₃Re(Br)(Ph₂P(CH₂)₆C≡CCH₃)₂ ( 5 ), (η⁵‐C₅H₅)Ru(Cl)(Ph₂P(CH₂)₆C≡CCH₃)₂ ( 6 ), and trans‐(Cl)(C₆F₅)Pt(Ph₂P(CH₂)₆C≡CCH₃)₂ ( 7 ). Alkyne metatheses with the catalyst (t‐BuO)₃W(≡C‐t‐Bu) (10–15 mol %, chlorobenzene, 80 °C) give the seventeen‐membered metallamacrocycles fac‐(CO)₃Re(Br)(Ph₂P(CH₂)₆CC(CH₂)₆P Ph₂) ( 8 ), (η⁵‐C₅H₅)Ru(Cl)(Ph₂P(CH₂)₆CC(CH₂)₆P Ph₂) ( 9 ), and trans‐(Cl)(C₆F₅)Pt(PPh₂(CH₂)₆CC(CH₂)₆P Ph₂) ( 10 ). ³¹P NMR analyses show 90–75% conversions to 8 – 10 (59–47% isolated after chromatography). The identity of 8 was confirmed by a crystal structure, and 10 was hydrogenated over Pd/C to fac‐(CO)₃Re(Br)(Ph₂P(CH₂)₆CC(CH₂)₆P Ph₂) ( 12 , 87%), which was crystallographically characterized earlier. A catalyst derived from Mo(CO)₆/4‐chlorophenol effects a slower conversion of 7 to 10 at 140 °C. In the case of 5 , a mer, trans isomer of 8 is isolated ( 11 , 44%), as established by NMR and IR data. In 10 – 12 , the diphosphines span trans positions. These results, together with previous examples involving group VIII metallocenes, establish the wide viability of the title reaction.     

Cooperative effect between iridium and platinum in the carbonylation of methanol to acetic acid

The iodocarbonyl monomer [PtI₂(CO)₂] 7 promotes the iridium catalyzed carbonylation of methanol to acetic acid at low water contents. Studies based on low pressure or high pressure NMR and the use of labeled reactants were conducted close to the real conditions of catalysis in order to get a deeper insight into this system. Carbonylation of CH₃I at low water contents proceeds slowly and the migratory CO insertion step, leading from H[IrI₃(CH₃)(CO)₂] 2-H to H[IrI₃(COCH₃)(CO)₂] 6-H is rate limiting. The dimer [PtI₂(CO)]₂ 7′ reacts immediately with [PPN][IrI₃(CH₃)(CO)₂] 2-PPN (PPN is Ph₃P=N⁺=PPh₃) under nitrogen to afford a mixture of species, among which the key heterobinuclear [Ir–Pt] intermediate [PPN][IrI₂(CH₃)(CO)₂(μ-I)PtI₂(CO)] 8-PPN has been identified; [PPN][IrI₂(CH₃)(CO)₂(μ-I)PtI₂(CO)] 8-PPN can in its turn lead to the formation of [PPN][PtI₃(CO)] 9-PPN, [IrI₂(CH₃)(CO)₂(solv)] 10, [Ir₂I₂(CH₃)₂(μ-I)₂(CO)₄] 3′ and [PPN][Ir₂I₄(CH₃)₂(μ-I)(CO)₄] 11-PPN; all of these species have been characterized. Under CO pressure, [PPN][IrI₂(CH₃)(CO)₂(μ-I)PtI₂(CO)] 8-PPN is a short-lived species that quickly leads to [IrI₂(CH₃)(CO)₃] 4 and [PPN][PtI₃(CO)] 9-PPN showing that the main role of the platinum promoter is to abstract an I⁻ ligand from [PPN][IrI₃(CH₃)(CO)₂] 2-PPN. Under catalytic conditions, I⁻ is abstracted from H[IrI₃(CH₃)(CO)₂] by [PtI₂(CO)₂] 7 and the rate determining step is accelerated; the relevant species H[IrI₃(CH₃)(CO)₂] 2-H, H[IrI₃(COCH₃) (CO)₂] 6-H and H[PtI₃(CO)] 9-H have been observed under 30 bar of CO. A catalytic cycle is proposed, which depicts the cooperative effect between the iridium catalyst and the platinum promoter.     

FTIR spectroscopic evidence of formation of geminal dinitrogen species during the low-temperature N2 adsorption on NaY zeolites

Adsorption of N₂ on NaY zeolites at 85 K and equilibrium pressures higher than 1 kPa results in the formation of geminal dinitrogen complexes characterized by an IR band at 2333.5 cm⁻¹ (2255.4 cm⁻¹ after adsorption of ¹⁵N₂). With decreasing equilibrium pressure the complexes tend to loose one N₂ ligand, thus forming linear species characterized by an IR band at 2336.8 cm⁻¹ (2258.7 cm⁻¹ after adsorption of ¹⁵N₂). All species disappear completely after evacuation. Co-adsorption of N₂ and CO revealed that the dinitrogen complexes are formed on Na⁺ cations. The changes in the concentrations of the linear and geminal N₂ species with the changes in the equilibrium pressure are excellently described by equations of adsorption isotherms proposed earlier for mono- and di-carbonyls. This revised version was published online in July 2006 with corrections to the Cover Date.     

Organometallic Rhodium Complexes Encapsulated in Mesoporous Molecular Sieves

Rh(III) complexes both dimmer [Cp*RhCl]₂(μ-Cl)₂ and monomer ([RhCp*(S)₃]²⁺) were encapsulated into MCM-41 channels. All silica MCM-41 molecular sieve and aminosililated MCM-41 matrix were used for rhodium complexes accommodation. Reactivity of Cp* rhodium complexes encapsulated in meso structure was estimated on the grounds of their susceptibility to interaction with CO molecules resulting in the formation of carbonyl complexes. Formation of Cp*Rh carbonyls was recorded by means of FTIR spectra. It was found that accommodation of Rh(III) complexes in MCM-41 molecular sieves activated the complex and led to the formation of Rh(III)Cp* carbonyls as a result of contact with CO. Contact of rhodium (III) complexes encapsulated in MCM-41 matrix with CO did not result in rhodium (III) reduction, whereas in the presence of amine groups in aminosililated MCM-41 the reduction of Rh(III) to Rh(I) occurred relatively easily and formation of Cp*Rh(CO)₂ complex containing Rh(I) was noted. Encapsulated rhodium complexes showed some activity in methanol carbonylation reaction carried out under heterogeneous conditions. For the most active catalyst the amount of methyl acetate reached about 8 mol.%, however, deactivation of catalyst occurred and after 2 h on stream methyl acetate was not found in the product.     

Plasma enhanced chemical deposition of nanocrystalline silicon carbonitride films from trimethyl(phenylamino)silane

Synthetic process for nanocrystalline silicon carbonitride films was developed using plasma-chemical decomposition of a new organosilicon reagent, namely, trimethyl(phenylamino)silane Me₃SiNHPh. Synthesis was carried out from the gaseous mixtures, such as Me₃SiNHPh + He, Me₃SiNHPh + N₂, and Me₃SiNHPh + NH₃, in a reactor in the wide temperature range (473–973 K) under the low pressure (4–5 × 10⁻² Torr). Polished wafers of Si(100), Ge(111), and silica glass were used as substrates. Dependences of the chemical and phase compositions, the surface morphology, and the silicon carbonitride optical properties on the process temperature were studied using FTIR and Raman spectroscopy, energy dispersive spectroscopy (EDS), atomic force microscopy (AFM), scanning electron microscopy (SEM), ellipsometry, and spectrophotometry.     

Catalytic Conversions in Aqueous Media. Part 2. A Novel and Highly Efficient Biphasic Hydrogenation of Renewable Methyl Esters of Linseed and Sunflower Oils to High Quality Biodiesel Employing Rh/TPPTS Complexes

An unusual high catalytic activity (TOF = 117,000 h⁻¹) and high catalyst productivity (TON = 9,700) have been achieved in the first example of partial hydrogenation of renewable polyunsaturated crude methyl esters of linseed and sunflower oils catalyzed by water soluble Rh/TPPTS complexes [TPPTS = P(C₆H₄-m-SO₃Na)₃] in aqueous/organic two-phase systems to afford monounsaturated fatty esters which is biodiesel first generation of improved oxidative stability, energy and environmental performance at a low pour point. This exceptionally high catalytic activity contrast with the general perception that industrially applied water soluble Rh/TPPTS catalysts normally exhibit very low rates in the conversions of higher molecular weight starting materials in aqueous/organic two-phase systems. For part 1 of this series see Ref. [14].     

Homogeneous catalytic hydrogenation of canola oil using a ruthenium catalyst

Dichlorodicarbonylbis (triphenylphosphine) ruthenium (II), RuCl₂ (CO)₂ (PPh₃)₂, was investigated as a catalyst for edible oil hydrogenation in a preliminary screening of potential catalysts for producing partially hydrogenated fats with lowtrans-isomer content. Refined, bleached and deodorized canola oil was hydrogenated using 1.77 × 10⁻⁵ − 6.64 × 10⁻⁴ mol/kg-oil of ruthenium catalyst equivalent to 1.79 × 10⁻⁴ − 6.71 × 10⁻³ wt% Ru. The effects of temperature (50–180 C) and pressure (50–750 psig) on reaction rate,trans-isomer content and fatty acid composition were examined. The activities of RuCl₂ (CO)₂ (PPh₃)₂ and nickel (Nysel HK-4 and AOCS standard nickel catalyst) were compared on a molar basis. At 4.40 × 10⁻⁴ mol/kg-oil (0.0026 wt/Ni or 0.0044 wt% Ru), 140 C and 50 psig, the nickel catalysts were completely inactive, but the ruthenium catalyst produced an IV drop of 40 units in 60 min. At 110 C, 750 psig and 1.34 × 10⁻⁴ mol/kg-oil (1.35 × 10⁻³ wt% Ru), a hydrogenation rate of 0.89 ΔIV/min and a maximumtrans-isomer content of 10.4% (IV=45.0) was obtained with the ruthenium catalyst.     

Formation of [8,8-η2-{(μ-Cl)2Ru(η6-p-cym)Ph2PCH2PPh2}-nido-8,7-RhSB9H10], a bimetallic derivative of the novel species [8,8-(η2-dppm)-8-(η1-dppm)-nido-8,7-RhSB9H10]

Treatment of [8,8-(η²-dppm)-8-(η¹-dppm)-nido-8,7-RhSB₉H₁₀] (I) with [Ru(η⁶-p-cym)Cl₂]₂ leads to the formation of a new bimetallic complex, [8,8-η²-{(μ-Cl)₂Ru(η⁶-p-cym)Ph₂PCH₂PPh₂}-nido-8,7-RhSB₉H₁₀], (II) containing the group [(μ-Cl)₂Ru(η⁶-p-cym)Ph₂PCH₂PPh₂] that coordinates in a multidentate mode to Rh.