Interactions of rhodium carbonyl compounds supported on inorganic oxides with CO,H2 and propylene

RhCl(CO)(PPh₃)₂, RhH(CO)(PPh₃)₃, and [RhClfCO)₂]₂ were supported on silica gel, γ-alumina, titania.and magensia in 3 to 5 wt % to study the interactions of rhodium carbonyl with the surface of inorganic oxides When trans-RhCI(CO)(PPh₃)₂ was supported on the surface of silica gel, cis-RhCl(CO) (PPh₃)₂ species was detected via the splitting of the CO infra red stretching band of trans-RhCI (CO)(PPh₃)₂. With other supports, same phenomenon was observed but with the different pattern of intensities of the splitted CO stretching bands. RhH(CO)(PPh₃)₃ was easily decarbonylated, after interacting with the surface of silica gel, γ-alumina, and titania. However, [RhCl(CO)₂]₂ was decarbonylated on the surface of inorganic oxides mentioned above and most of supported [RhCl(CO)₂]₂ converted to a stable surface carbonyl species [M-OH-RhCI(CO)₂; M = Si, Al, Ti]. Diffuse reflectance infrared spectroscopy (DRS) was used to study the interactions of 5 wt % RhCl(CO)(PPh₃)₂ supported on silica gel with H₂, CO and/or propylene at various temperatures. The result indicated that the surface intermediates formed from the interaction of RhCl(CO)(PPh₃)₂ with CO, H₂ and C₃H₆ were not identical to the corresponding liquid-phase intermediates of RhCl(CO)(PPh₃)₂ in the presence of solvent.     

Preparation of conjugated soybean oil and other natural oils and fatty acids by homogeneous transition metal catalysis

The use of as little as 0.1 mol% [RhCl(C₈H₁₄)₂]₂, 0.25 mol% PtCl₂(PPh₃)₂, or 0.5 mol% RuHCl(CO)(PPh₃)₃, where Ph = phenyl, catalyzes the isomerization of soybean oil to conjugated soybean oil under mild reaction conditions and in high yields. No hydrogenation products are detected with any of these catalysts. Preliminary physical tests have shown that the conjugated soybean oil has exceptional drying properties and the resulting coatings exhibit good solvent resistance. The [RhCl(C₈H₁₄)₂]₂ catalyst provides similarly high yields of other conjugated vegetable oils, conjugated linoleic acid, and conjugated ethyl linoleate. Other rhodium catalysts, such as RhCl(PPh₃)₃, have also been found to be effective for the conjugation of ethyl linoleate.     

Hydroformylation of olefins with water-soluble rhodium catalysts in the presence ofα-cyclodextrin

Hydroformylation of hex-1-ene using a water soluble rhodium catalyst HRh(CO)[PPh₂(m-C₆H₄SO₃Na)]₃ (HRh(CO)(TPPMS)₃) (I), gives lower yields when-cyclodextrin is added to the biphasic reaction system implying an interaction between the cyclodextrin and rhodium catalyst.     

Solvent/C60 exchange on Ir(CO)(PPH3)2(Cl)(η2-C60) and solvent/solvent’ exchange on Ir(CO)(PPH3)2(Cl)(solvent)

Dissociation of C₆₀ from Ir(CO)(PPh₃)₂(Cl)(η²-C₆₀) in a binary mixture of solvents (solvent₁ and solvent₂) produced non-equilibrium mixtures of Ir(CO)(PPh₃)₂(Cl)(solvent₁) and Ir(CO)(PPh₃)₂(Cl)(solvent₂). Once the solvated species were produced, they underwent a relative fast solvent exchange between them to produce an equilibrium mixture.     

Rapid isomerization of allylic alcohols with iridium(I) and rhodium(I) complexes at ambient temperature

Among allylic alcohols, but-3-en-2-ol is most rapidly isomerized to give butan-2-one in the presence of Ir(ClO₄)(CO)(PPh₃)₂ while 2-methylprop-2-en-1-ol most rapidly undergoes the isomerization to give 2-methylpropanal in the presence of Rh(ClO₄)(CO)(PPh₃)₂ at room temperature under hydrogen.     

Migratory insertion reaction in alkenyl ruthenium(II) complexes containing a trifluoroacetate ligand. X-ray structure of the Ru(η2- O2CCF3)(η1-OCCHCHtBu)(CO)(PPh3)2 complex

Reaction of compound Ru(O₂CCF₃)(CHCH^tBu)(CO)(PPh₃)₂ with CO gives the η¹-alkeneacyl complex Ru(O₂CCF₃)(OCCHCH^tBu)(CO)(PPh₃)₂, which is in equilibrium with the dicarbonyl Ru(O₂CCF₃)(CHCH^tBu)(CO)₂(PPh₃)₂ derivative in CH₂Cl₂ solution. The η¹-acyl form involves an η¹-coordination of the O₂CCF₃ ligand, whereas the dicarbonyl form contains the carboxylate ligand η²-coordinated to the metal. The same mixture of carbonylated compounds can be obtained from the reaction of Ru(CHCH^tBu)Cl(CO)₂(PPh₃)₂ with Na[O₂CCF₃] in a CH₂Cl₂/MeOH solution. These reactions reveal the significance of ancillary bidentate ligands for the η-nature of the acyl–metal bond. The molecular structure of the complex Ru(O₂CCF₃)(OCCHCH^tBu)(CO)(PPh₃)₂ was established by X-ray diffraction study of a monocrystal obtained from a CH₂Cl₂/MeOH solution of the mixture of carbonylated compounds.     

A new octahedral,liquid-crystalline complex containing a bulky ruthenium fragment

The reaction of RuClH(CO)(PPh₃)₃ with HO₂CC₆H₄-p-O₂CC₆H₄-p-O(CH₂)₃CH₃ gives the complex RuCl(O₂CC₆H₄-p-O₂CC₆H₄-p-OBu)(CO)(PPh₃)₂. The crystal structure shows, in the solid state, molecules of the complex ordered parallel to one another giving layers. This compound has a bulky metallic fragment but however shows a calamitic liquid crystal behavior induced by the carboxylate ligand.     

Preparation of Ru(η3-2-alkenylallyl)(CO)Cl(PPh3)2 complexes via carbometallation of allenes with alkenyl ruthenium complexes

Alkenyl ruthenium complex, Ru(CHCHR)(Cl)(CO)(PPh₃)₂ 1, reacted with allenes 2 to give η³-allyl ruthenium complexes, Ru(η³-2-alkenylallyl)(Cl)(CO)(PPh₃)₂ 3, in good yields. The reaction depends on the structure of the alkenyl group. When R was phenyl or methoxycarbonyl group, the carbometallated complex 3 was yielded as a sole product. However, when R was butyl or trimethylsilyl group, besides the carbometallation product as main product, was obtained a small amount of 2-unsubstituted η³-allyl ruthenium complex which was formed via β-elimination of the alkenyl complex followed by the reaction with allene. Structure of 3 was determined by the X-ray crystal structure analysis.     

Photoluminescence and photochemistry of Pt(II)(PPh3)2(C6O6) induced by rhodizonate IL excitation

The complex Pt(II)(PPh₃)₂(C₆O₆) was prepared by the reaction of Ag₂C₆O₆ with cis-Pt(PPh₃)₂Cl₂ in acetonitrile. Pt(PPh₃)₂(C₆O₆) is characterized by a lowest-energy IL (rhodizonate) excited state. The complex shows an IL fluorescence, but is also photoactive. The photolysis leads to the conversion of rhodizonate to croconate in the coordinated state: Pt(II)(PPh₃)₂(C₆O₆) → Pt(II)(PPh₃)₂(C₅O₅) + CO.     

The formation of σ-phenylethynyl and σ-diphenylbutenynyl complexes in the reaction of σ-alkenyl ruthenium(II) complexes with phenylacetylene. The X-ray structure of a ruthenium(II) complex containing a σ-phenylethynyl ligand

Ruthenium(II) complexes containing both σ-alkenyl and η²-carboxylate ligands Ru(O₂CR²)(CHCHR¹)(CO)(PPh₃)₂ (R¹^tBu, Ph; R²=CHCHCHCHCH₃) react with phenylacetylene in two stages. Their reaction with an equivalent amount of the alkyne led to the formation of a σ-alkynyl-containing ruthenium(II) complex Ru(O₂CR²)(CCPh)(CO)(PPh₃)₂ (R²=CHCHCHCHCH₃), the molecular structure of which was established by X-ray diffraction. This σ-alkynyl complex then reacts with phenylacetylene to form a σ-butenynyl-containing compound Ru(O₂CR²)(C(CCPh)CPhH)(CO)(PPh₃)₂ (R²=CHCHCHCHCH₃). Both reactions support the key role of alkynyl ligands in the dimerization of alkynes.     

Diastereotopic relationship between planar and central chiralities in the formation of Ru(η3-allyl)(CO)(PPh3)(L–L′) complexes

Hydride ruthenium complexes, RuHCl(CO)(PPh₃)₂(L–L^′) 3 (L–L^′=bidentate ligand having nitrogen and oxygen) react with allenes to give Ru(η³-allyl)(CO)(PPh₃)(L–L^′) complexes 5 in good yields via hydrometalation reaction. The complexes 5 have planar chirality at the η³-allyl ligand and central chirality at the Ru metal, and consist of one pair of enantiomers. Ligand substitution reaction of Ru(η³-allyl)Cl(CO)(PPh₃)₂ complexes 6 with bidentate ligands (L–L^′) also afford the complexes 5 which have the same stereochemistry as those formed by the hydrometalation reaction. The planar chirality is controlled by the central chirality at the Ru metal in both the formations of the complexes 5. The structure of 5a (L–L^′=N–N bidentate ligand) was determined by the X-ray crystal structure analysis.     

Improved Syntheses of Versatile Ruthenium Hydridocarbonyl Catalysts Containing Electron‐Rich Ancillary Ligands

Clean, high‐yield routes are established to the important catalyst chlorobis(tricyclohexylphosphine)ruthenium hydridocarbonyl [RuHCl(CO)(PCy₃)₂] 2 and its N‐heterocyclic carbene (NHC) derivatives RuHCl(CO)(NHC)(PCy₃) ( 3a : NHC=IMes; 3b , NHC=H₂IMes; IMes=1,3‐dimesitylimidazol‐2‐ylidene). These complexes are obtained by treating chlorotris(tricyclohexylphosphine)ruthenium hydridocarbonyl [RuHCl(CO)(PPh₃)₃] 1 with tricyclohexylphosphine [PCy₃], or with the appropriate NHC ligand, then PCy₃. Advantages over prior routes to these complexes lie in the high yields from a conveniently accessible precursor, the absence of by‐products that otherwise prove difficult to remove, and the short reaction times under experimentally convenient conditions.     

Rhodium‐Catalyzed Highly Regioselective Hydroformylation‐Hydrogenation of 1,2‐Allenyl‐Phosphine Oxides and ‐Phosphonates

The rhodium‐catalyzed hydroformylation‐hydrogenation of 1,2‐allenyl‐phosphine oxides and ‐phosphonates is reported in this paper. The regioselectivity was well controlled, affording only saturated linear γ‐phosphinyl aldehydes under the standard conditions: (carbonyl)tris(triphenylphosphine)‐rhodium hydride [RhH(CO)(PPh₃)₃] (3 mol%), triphenylphosphine (PPh₃) (10 mol%), carbon monoxide (CO) (2.4×10⁶ Pa), hydrogen (H₂) (subsequently charged to 4.8×10⁶ Pa), toluene, 100 °C, 24 h.     

Heterogenized HRh(CO)(PPh3)3 on zeolite Y using phosphotungstic acid as tethering agent: a novel hydroformylation catalyst

Heterogenization of HRh(CO)(PPh₃)₃ tethered through phosphotungstic acid to zeolite Y support, gives a novel hydroformylation catalyst with excellent stability, reusability and even improved activity. The activity, selectivity and stability of this catalyst for hydroformylation of a variety of linear and branched olefinic substrates have been demonstrated. The heterogenized HRh(CO)(PPh₃)₃ catalyst was recycled several times without loss of any activity. The catalyst was characterized by powder XRD, SEM, XPS, and ³¹P CP MAS NMR to establish true heterogeneity and morphological characteristics.     

Immobilization of HRh(CO)(P(m-C6H4SO3Na)3)3 on an anion exchange resin for the hydroformylation of higher olefins

The anion exchange resin Amberlyst, A-26, forms an efficient matrix for the immobilization of the water soluble complex, HRh(CO)(m-C₆H₄SO₃Na)₃)₃. Catalysis proceeds in anhydrous alcohol solvents which allows the conversion of water insoluble olefins to aldehydes. Activities and selectivities are similar to both supported aqueous phase catalysts and to the neutral complex, HRh(CO)(PPh₃)₃ in non-aqueous solvents. The catalyst preparation minimizes the quantity of water in the supported catalyst; the lack of water is thought to be responsible for an increase in catalyst stability toward oxidation.     

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 palladium complex catalyst in the synthesis of N,N′-diphenylurea from nitrobenzene,aniline and carbon monoxide

A catalyst system comprising palladium acetate and bidentate bis(diphenylphosphino)alkane ligand of general formula Ph₂P(CH₂)_nPPh₂ (n = 3–5) was highly active in N,N-diphenylurea synthesis from nitrobenzene, aniline and carbon monoxide and showed different reactivity from the system with the more common monodentate triphenylphosphine ligand.     

UV laser desorption/ionisation mass spectrometry of the triruthenium clusters Ru3(CO)12−n(PPh3)n (n=1, 2 and 3)

The negative ion ultraviolet laser desorption mass spectra of Ru₃(CO)₁₂ and its triphenylphosphine derivatives Ru₃(CO)_12−n(PPh₃)_n (n=1–3) have been recorded using laser desorption/ionisation time-of-flight mass spectrometry (LDI-TOF-MS). The spectra contain peaks in the parent region together with peaks at higher masses due to extensive gas phase reactions. Substitution of one to three carbonyls by the bulky triphenylphosphine ligand has a number of interesting effects on the spectra, most notably, increasing the degree of coordinative unsaturation of the gas phase clusters in the molecular ion region and increasing the intensity of the subsequent high mass reaction products.     

Rhodium complexes as catalysts for hydrosilylation crosslinking of silicone rubber

Vulcanization of silicon rubber compound based on polysiloxanes containing vinyl and Si–H groups catalyzed by [RhCl(CO)₂]₂, [RhCl(C₂H₄)₂]₂, [RhCl(1,5-COD)]₂, [RhCl(NBD)]₂, RhCl[P(C₆H₅)₃]₃, and Rh(acac)₃ (1,5-COD = 1,5-cyklooktadiene, NBD = norbornadiene, acac = acetylacetonate) has been studied in dependence on the catalyst, solvent, and reaction conditions. The course of vulcanization as well as the crosslinking density of the vulcanizate and the content of sol indicate that the above catalysts are comparable to and in some cases even better than the widely used hexachloroplatinic acid.     

Hydroformylation of 1-octene using rhodium–phosphite catalyst in a thermomorphic solvent system

The use of a liquid–liquid biphasic thermomorphic or temperature-dependent multicomponent solvent (TMS) system, in which the catalyst accumulates in one of the liquid phases and the product goes preferably to the other liquid phase, can be an enabling strategy of commercial hydroformylation processes with high selectivity, efficiency and ease of product separation and catalyst recovery. This paper describes the synthesis of n-nonanal, a commercially important fine chemical, by the hydroformylation reaction of 1-octene using a homogeneous catalyst consisting of HRh(PPh₃)₃(CO) and P(OPh)₃ in a TMS-system consisting of propylene carbonate (PC), dodecane and 1,4-dioxane. At a reaction temperature of 363 K, syngas pressure of 1.5 MPa and 0.68 mM concentration of the catalyst, HRh(CO)(PPh₃)₃, the conversion of 1-octene and the yield of total aldehyde were 97% and 95%, respectively. With a reaction time of 2 h and a selectivity of 89.3%, this catalytic system can be considered as highly reactive and selective compared to conventional ones. The resulting total turnover number was 600, while the turnover frequency was 400 h^?1. The effects of increasing the concentration of 1-octene, catalyst loading, partial pressure of CO and H₂ and temperature on the rate of reaction have been studied at 353, 363 and 373 K. The rate was found to be first order with respect to concentrations of the catalyst and 1-octene, and the partial pressure of H₂. The dependence of the reaction rate on the partial pressure of CO showed typical substrate inhibited kinetics. The kinetic behavior differs significantly from the kinetics of conventional systems employing HRh(CO)(PPh₃)₃ in organic solvents. Most notable are the lack of olefin inhibition and the absence of a critical catalyst concentration. A mechanistic rate equation has been proposed and the kinetic parameters evaluated with an average error of 5.5%. The activation energy was found to be 69.8 kJ/mol.