The reaction of trichlorosilyltetracarbonyliron hydride (HFe(CO)4SiCl3) with conjugated dienes

Isoprene, 1,3-butadiene and 2,3-dimethyl-1,3-butadiene react with HFe(CO)₄SiCl₃ by addition of the Fe---H function to the diene. Isoprene appears to add predominantly 1,4 and 2,3-dimethyl-1,3-butadiene appears to add 1,2, while 1,3-butadiene may add both ways. In the case of isoprene and 1,3-butadiene loss of CO from the addition compound gives a stable π-allyl- Fe(Co)₃SiCl₃ product. Either cis- or trans-1,3-pentadiene is reduced to pentene by HFe(CO)₄SiCl₃.     

Structural studies of Rh4(CO)12 derivatives in solution and in the solid state

The crystal structures of Rh₄(CO)₁₀(PPh₃)₂ and Rh₄(CO)₉P(OPh)₃₃ are reported. ³¹P-¹H NMR studies on Rh₄(CO)₁₂-_x {P(OPh)₃}_x(X  1, 2 and 3) show that each derivative exists as only one isomer in solution whereas the analogous triphenylphosphine derivatives can exist as different isomers. A quantitative redistribution of triphenylphosphites occurs on mixing Rh_4-(CO)₁₂-_xL_x with Rh₄(CO)₁₂-_yL_y (L  P(OPh)₃; x  0, 1, 2, y  x + 2; x  0, y  x + 4) to give Rh₄(CO)₁₂-_zL_z[z $\text{1}\text{2}$(x + y)]; a related rapid intermolecular randomisation of carbonyls occurs on mixing Rh₄(¹²CO)₁₂ with Rh₄(¹³CO)₁₂.     

New Bimetallic Ni–Rh Carbonyl Clusters: Synthesis and X-ray Structure of the [Ni7Rh3(CO)18]3?, [Ni3Rh3(CO)13]3? and [NiRh8(CO)19]2? Cluster Anions

The reaction of the [Ni₆(CO)₁₂]²⁻ dianion with [Rh(COD)Cl]₂ (COD = cyclooctadiene) in acetone affords a mixture of bimetallic Ni–Rh clusters, mainly consisting of the new [Ni₇Rh₃(CO)₁₈]³⁻ and [Ni₈Rh(CO)₁₈]³⁻ trianions. A study of the reactivity of [Ni₇Rh₃(CO)₁₈]³⁻ led to isolation of the new [Ni₃Rh₃(CO)₁₃]³⁻ and [NiRh₈(CO)₁₉]²⁻ anions. All these new bimetallic Ni–Rh carbonyl clusters have been isolated in the solid state as tetrasubstituted ammonium salts and have been characterised by elemental analysis, X-ray diffraction studies, ESI-MS and electrochemistry. The unit cell of the [NEt₄]₃[Ni₇Rh₃(CO)₁₈] salt contains two orientationally-disordered ν₂-tetrahedral [Ni₇Rh₃(CO)₁₈]³⁻ trianions with occupancy factors of 0.75 and 0.25. Besides, their inner Ni₃Rh₃ octahedral moieties show two cis sites purely occupied by Rh atoms, two trans sites purely occupied by Ni atoms and the remaining two cis sites are disordered Ni and Rh sites with respective occupancy fraction of 0.5. At difference from the parent [Ni₇Rh₃(CO)₁₈]³⁻, the octahedral [Ni₃Rh₃(CO)₁₃]³⁻ displays an ordered distribution of Ni and Rh atoms in two staggered triangles. The [NiRh₈(CO)₁₉]²⁻ dianion adopts an isomeric metal frame with respect to that of the [PtRh₈(CO)₁₉]²⁻ congener. As a fallout of this work, new high-yield synthesis of the known [Ni₆Rh₃(CO)₁₇]³⁻ and [Ni₆Rh₅(CO)₂₁]³⁻, as well as other currently-investigated bimetallic Ni–Rh clusters have been obtained.     

Surface supported metal cluster carbonyls. Chemisorption decomposition and reactivity of Rh4(CO)12 supported on silica and alumina

Chemisorption of Rh₄(CO)₁₂ on to a highly divided silica (Aerosil “0” from Degussa), Leads to the transformation: 3 Rh₄(CO)₁₂ → 2 Rh₆(CO)₁₆ + 4 CO. Such an easy rearrangement of the cluster cage implies mobility of zerovalent rhodium carbonyl fragments on the surface. Carbon monoxide is a very efficient inhibitor of this reaction, and Rh₄(CO)₁₂ is stable as such on silica under a CO atmosphere. Both Rh₄(CO)₁₂ and Rh₆(CO)₁₆ are easily decomposed to small metal particles of higher nuclearity under a water atmosphere and to rhodium(I) dicarbonyl species under oxygen. From the Rh^I(CO)₂ species it is possible to regenate first Rh₄(CO)₁₂ and then Rh₆(CO)₁₆ by treatment with CO (P_co ? 200 mm Hg) and H₂O (P_H2O ? 18 mm Hg). The reduction of Rh^I(CO)₂ surface species by water requires a nucleophilic attack to produce an hypothetical [Rh(CO)_n]_m species which can polymerize to small Rh₄ or Rh₆ clusters in the presence of CO but which in the absence of CO lead to metal particles of higher nuclearity. Similar results are obtained on alumina.     

Effect of LaFeO3 Decoration and Ozone Treatment on Thermal Stability of Au/Al2O3 for CO Oxidation

The 1.1%Au/LaFeO_x/Al₂O₃ catalysts were prepared by the iso-volume impregnation method and activated with H₂ or O₃. The catalytic performance for CO oxidation at room temperature was investigated by accelerated deactivation tests in 1.0% CO reactant stream at 550 °C. The introduction of La and Fe enhanced the thermal stability of Au/Al₂O₃ with a decrease in initial activity, probably due to the formation of LaFeO₃ perovskite on the Al₂O₃ surface. The 1.1%Au/2%LaFeO₃/Al₂O₃ catalyst activated by H₂ can transform 65% CO into CO₂ at room temperature after pretreatment in 1.0% CO reactant stream at 550 °C for 2 h, whereas 1.1%Au/Al₂O₃ activated by H₂ totally loses its activity. O₃ activation can always make 1.1%Au/LaFeO₃/Al₂O₃ more active than that of H₂ activation during the pretreatment process in 1.0% CO. After pretreatment for 10 h, 1.1%Au/2%LaFeO₃/Al₂O₃ activated by O₃ still shows 40% conversion of 1.0% CO at room temperature, whereas those activated by H₂ become inactive completely. The better thermal stability of the catalysts activated by O₃ may be due to that O₃ activation leads to the formation of partially oxidized state of Au in Au/FLA-O₃, which may reinforce the interaction between the metal and support.     

Catalytic asymmetric synthesis of descurainin via 1,3-dipolar cycloaddition of a carbonyl ylide using Rh2(R-TCPTTL)4

A catalytic asymmetric synthesis of descurainin has been achieved by incorporating an enantioselective 1,3-dipolar cycloaddition, a stereoselective alkene hydrogenation, an oxidation with Fremy’s salt and a regioselective demethylation with NbCl₅ as the key step. The 1,3-dipolar cycloaddition of a carbonyl ylide derived from tert-butyl 2-diazo-5-formyl-3-oxopetanoate with 4-hydroxy-3-methoxyphenylacetylene in the presence of dirhodium(II) tetrakis[N-tetrachlorophthaloyl-(R)-tert-leucinate], Rh₂(R-TCPTTL)₄, provided an 8-oxabicyclo[3.2.1]octane skeleton in 95% ee.     

A synthetic route to heteronuclear clusters containing iridium and rhodium: X-ray crystal structures of [IrOs3(μ-H)2(μ-Cl)(CO)12] and [Ir2Rh2(μ-CO)(μ3-CO)2(CO)4(η-C5Me5)2]

The iridium and rhodium complexes [MCl(CO)₂(NH₂C₆H₄Me-4)] (M = Ir or Rh) react with [Os₃(μ-H)₂(CO)₁₀] to give the tetranuclear clusters [MOs₃(μ-H)₂(μ-Cl)(CO)₁₂]; the iridium compound being structurally identified by X-ray diffraction. Similarly, [IrCl(CO)₂(NH₂C₆H₄Me-4)] and [Rh₂(μ-CO)₂(η-C₅Me₅)₂] afford the tetranuclear cluster [Ir₂Rh₂(μ-CO)(μ₃-CO)₂(CO)₄(η-C₅Me₅)₂], also characterised by single-crystal X-ray crystallog     

Synthesis and DFT Defined trans (O5O6) Molecular Structure of Cs[Fe(1,3- pddadp )] · 2H2O. Strain Analysis and Spectral Assignment of the Complex

Summary. An iron(III) complex with the hexadentate ligand 1,3-propanediamine-N,N′-diacetate-N,N′-di-3-propionate (1,3-pddadp) was prepared, chromatographically isolated as its isomer trans(O₅O₆)-Cs[Fe(1,3-pddadp)] · 2H₂O, and characterized. The trans(O₅O₆) configuration of the iron(III) compound was found to dominate and this geometry was established by means of IR spectroscopy and Density Functional Theory (DFT). Structural data correlating the octahedral geometry of the [Fe(1,3-pddadp)]⁻ unit and an extensive strain analysis are discussed in relation to the information obtained for similar complexes. Antibacterial activities of the free ligand and its corresponding iron(III) complex towards common Gram-negative and Gram-positive bacteria are reported as well.     

Synthesis and DFT Defined trans (O5O6) Molecular Structure of Cs[Fe(1,3- pddadp )] · 2H2O. Strain Analysis and Spectral Assignment of the Complex

An iron(III) complex with the hexadentate ligand 1,3-propanediamine-N,N′-diacetate-N,N′-di-3-propionate (1,3-pddadp) was prepared, chromatographically isolated as its isomer trans(O₅O₆)-Cs[Fe(1,3-pddadp)] · 2H₂O, and characterized. The trans(O₅O₆) configuration of the iron(III) compound was found to dominate and this geometry was established by means of IR spectroscopy and Density Functional Theory (DFT). Structural data correlating the octahedral geometry of the [Fe(1,3-pddadp)]⁻ unit and an extensive strain analysis are discussed in relation to the information obtained for similar complexes. Antibacterial activities of the free ligand and its corresponding iron(III) complex towards common Gram-negative and Gram-positive bacteria are reported as well.     

Synthesis and molecular structure of [Au3Ru4(μ3-H)(CO)12(PPh3)3]

The title compound can be prepared in good yield by heating either [Ru₄(μ-H)₄(CO)₁₂] or [Au₂Ru₄(μ₃-H)₂(CO)₁₂(PPh₃)₂] with [AuMe(PPh₃)] in toluene. The related compound [Au₃Ru₄(μ₃-H)(μ-dppm)(CO)₁₂(PPh₃)] has also been prepared. Both trigoldtetraruthenium clusters undergo dynamic behaviour in solution, involving intramolecular rearrangement of the metal core, as revealed by variable temperature NMR studies. The crystal structure of [Au₃Ru₄(μ₃-H)(CO)₁₂(PPh₃)₃] has been established by an X-ray diffraction study. The metal atom core comprises a trigonal bipyramidal AuRu₄ unit with two AuRu₂ faces capped by gold atoms.     

Alkylation of toluene with 1,3-pentadiene catalyzed by [bupy]BF4-AlCl3 and [bupy]BF4-FeCl3 ionic liquids

A new application of ionic liquids is developed for a novel process of synthesizing pentyltoluene from toluene and a C5 diolefin (1,3-pentadiene). The catalyst [bupy]BF₄-AlCl₃ behaves better than [bupy]BF₄-FeCl₃.     

The reactions of Rh2(CO)4Cl2 with 1,5-cyclooctadiene and tetramethylallene. A combined in-situ vibrational spectroscopies, spectral reconstruction and DFT study

Reactions of Rh₂(CO)₄Cl₂ with 1,5-cyclooctadiene (COD) and tetramethylallene (TMA) were performed separately in anhydrous hexane under argon atmosphere. Multiple perturbations of Rh₂(CO)₄Cl₂, COD and TMA were also performed during the reactions. These two reactions were monitored by in-situ FTIR (FIR and MIR) and/or Raman spectroscopies and the collected spectra were further analyzed with BTEM family of algorithms. DFT calculations were performed to identify the organometallic species present. The known diene complex Rh₂(CO)₂Cl₂(η⁴-C₈H₁₂) and a new allene complex Rh₂(CO)₃Cl₂(η²-C₇H₁₂) were formed as the two primary organo-rhodium products. Their pure component spectra were reconstructed in the three characteristic regions of 200-680, 800-1360, and 1500-2200 cm⁻¹. Their relative concentrations were also obtained by the least square fitting of the carbonyl region 1500-2200 cm⁻¹. The present contribution shows the usefulness of combining in-situ spectroscopic measurements, BTEM analysis and DFT spectral prediction in order to analyze organometallic reactions at high dilution and identify the reaction products.     

Multinuclear NMR studies on substituted derivatives of Rh6(CO)16 in solution

Multinuclear NMR data (¹³C, ³¹P, ¹³C–{³¹P}, ¹³C–{¹⁰³Rh} and ³¹P–{¹⁰³Rh}) for a series of mono- and di-substituted derivatives of Rh₆(CO)₁₆ containing neutral two electron donor ligands [Rh₆(CO)₁₅L, (L=NCMe, py, cyclooctene, PPh₃, P(OPh)₃,1/2(μ₂,η¹:η¹-dppe)); Rh₆(CO)₁₄(LL), (LL=cis-CH₂=CMe-CMe=CH₂, dppm, dppe, (P(OPh)₃)₂)] are reported; these data show that the solid state structure is maintained in solution. Detailed assignments of the ¹³CO NMR spectra of Rh₆(CO)₁₅(PPh₃) and Rh₆(CO)₁₄(dppm) clusters have been made on the basis ¹³C–{¹⁰³Rh} double resonance measurements and the specific stereochemical features of the observed long range couplings in these clusters have been studied. The stereochemical dependence of ³J(P–C) for terminal carbonyl ligands is discussed and the values of ³J(P–C) are found to be mainly dependent on the bond angles in the P–Rh–Rh–C fragment; these data enable the fine structure of the complex multiplets in the ¹³C–{¹H} and ³¹P–{¹H} NMR spectra of Rh₆(CO)₁₄ (dppm) to be simulated. Variable temperature ¹³C–{¹H} NMR measurements on Rh₆(CO)₁₅(PPh₃) reveal the carbonyl ligands in this complex to be fluxional. The fluxional process involves exchange of all the CO ligands except the two terminal CO's associated with the rhodium trans to the substituted rhodium and can be explained by a simple oscillation of the PPh₃ on the substituted rhodium atom aided by concomitant exchange of the unique terminal CO on this rhodium with adjacent μ₃-CO's.     

CO2 fixation by hydrogenation over coprecipitated Co/Al2O3

CO₂ fixation by hydrogenation over coprecipitated 36 wt.% Co/Al₂O₃ has been studied under a range of reaction conditions to clarify the effects of reaction variables and to determine the kinetics and mechanism of the reaction. A comparison of the results with those reported for CO hydrogenation on the same catalyst indicates that, although product distributions of CO₂ and CO hydrogenation differ, the kinetics and mechanism are similar.     

Katalytische isomerisierung von heptenen mit IrX(CO)L2

1-, 2-cis-, 2-trans-, and 3-trans-heptenes (C₇)are isomerized either very slowly or not at all with IrX(CO)L₂ at 80°C in toluene and under N₂. However, under the conditions of hydrogenation fast isomerisation takes place. With IrCl(CO)L₂ as catalyst the rate of isomerisation decreases the order: 1-C₇ ∼ 2-cis-C₇ > 3-trans-C₇ > 2-trans-C₇. This sequence is independent of the ligand L in lrCl(CO)L₂, however, with a particular isomer the rate of isomerisation is a function of L in the order L = PPh₃ > P(C₆H₁₁)3 > P(OPh)₃.     

Influence of Fe3(CO)12 on the interaction of Re2(CO)10 with hydroxylated alumina surface

The interaction of Re₂(CO)₁₀ and Fe₃(CO)₁₂, and that of Re₂Fe(CO)₁₄ with alumina were studied during thermal treatment by FT-IR spectroscopy. The interaction of Re₂Fe(CO)₁₄ with alumina results in the formation of Re-tricarbonyls as in the Re₂(CO)₁₀ + Fe₃(CO)₁₂/Al₂O₃ system, even at room temperature. In the view of this fact, the possibility of the action of reactive Fe-monocarbonyls [Fe(CO)₅, Fe(CO)₄] on the Re₂(CO)₁₀ with appearance of a Re₂Fe(CO)₁₄ as a transient intermediate on the support, cannot be excluded.     

Hydroformylation reactions of the trans -Mo(CO)4( p -C5NH4SO3NA)2 complex in biphasic medium

Trans-bis(sodium pyridine-p-sulphonate)tetracarbonylmolybdenum(0) complex, (trans-Mo(CO)₄(p-PySO₃Na)₂, (1)) was used as a catalytic precursor for the 1-hexene hydroformylation reaction, in biphasic toluene/water medium (T = 100°C, syngas total pressure = 600 psi, pH₂/pCO = 1). Complex (1) showed good activity favoring the linear aldehyde. Likewise as other organic olefin substrates and with synthetic and real naphtha, good conversions to oxygenated products were obtained.     

Reactions of isonitriles with [Fe3(CO)12] and [Ru3(CO)12] monitored by electrospray mass spectrometry: structural characterisation of [Fe3(CO)10(CNPh)2] and [Ru4(CO)11(μ3-η-CNPh)2(CNPh)]

The reactions of [Fe₃(CO)₁₂] or [Ru₃(CO)₁₂] with RNC (R=Ph, C₆H₄OMe-p or CH₂SO₂C₆H₄Me-p) have been investigated using electrospray mass spectrometry. Species arising from substitution of up to six ligands were detected for [Fe₃(CO)₁₂], but the higher-substituted compounds were too unstable to be isolated. The crystal structure of [Fe₃(CO)₁₀(CNPh)₂] was determined at 150 and 298 K to show that both isonitrile ligands were trans to each other on the same Fe atom. For [Ru₃(CO)₁₂] substitution of up to three COs was found, together with the formation of higher-nuclearity clusters. [Ru₄(CO)₁₁(CNPh)₃] was structurally characterised and has a spiked-triangular Ru₄ core with two of the CNPh ligands coordinated in an unusual μ₃-η² mode.     

Kinetics of catalytic combustion in air over Pt/Al2O3/Al catalyst

Summary Catalytic combustion of toluene, propylene and CO over Pt/Al₂O₃ /Al catalyst was investigated. Strong inhibition effects are observed when the mixture of toluene, propylene and CO is oxidized. A reaction mechanism of catalytic combustion over Pt/Al₂O/Al is proposed. The results from kinetic models are in good agreement with the experimental data.     

The formation of a new mixed cobalt rhodium carbonyl from Co2(CO)8 and Rh4(CO)12: Infrared spectroscopic characterization under carbon monoxide pressure

The formation of a new compound, the most characteristic IR absorption bands of which appear at 2007 cm^-1 and 1956 cm^-1, has been in the reaction between Co₂(CO)₈ and Rh₄(CO)₁₂ under carbon monoxide pressure in a hydrocarbon medium. The same compound is also formed either by the reaction of Co₂(CO)₈ with [Rh(CO)₂Cl]₂ or by the reaction of Co₃Rh(CO)₁₂ with carbon monoxide. The new complex has not been isolated in a pure state, but the formula CoRh(CO)₇ is proposed on the basis of the stoichiometry of its formation and its physico-chemical properties. Equilibrium constants and thermo-dynamic parameters for the reaction 2 Co₂(CO)₈ + Rh₄(CO)₁₂  4 CoRh(CO)₇ have been estimated. Possible structures for the new complex are discussed on the basis of its IR spectrum.