Water-soluble Organometallic Complexes Research Articles

ChemInform Abstract: Acceptorless Dehydrogenative Condensation of o‐Aminobenzamides with Aldehydes to Quinazolinones in Water Catalyzed by a Water‐Soluble Iridium Complex [Cp*Ir(H2O)3][OTf]2.

A general and efficient method for the synthesis of quinazolinones via acceptorless dehydrogenative condensation of o-aminobenzamides with aldehydes in water has been accomplished. In the presence of [Cp*Ir(H2O)3][OTf]2, a variety of desirable products were obtained in high yields with high atom economy under environmentally benign conditions. Notably, this research will facilitate the progress of acceptorless dehydrogenative reactions in water catalyzed by water-soluble organometallic complexes.

ChemInform Abstract: Cyclodextrins and Their Applications in Aqueous‐Phase Metal‐Catalyzed Reactions

AbstractReview: 132 refs.

Cyclodextrins and their applications in aqueous-phase metal-catalyzed reactions

Abstract During these last years, cyclodextrins have greatly contributed to the development of catalytic processes in water. These cyclic oligosaccharides composed of 6(α), 7(β) or 8(γ) glucopyranose units improve the mass transfer in aqueous-organic two-phase systems and are useful compounds to design new catalysts. Thus, chemically modified cyclodextrins can be used to: (1) significantly increase the rate and selectivity of reactions catalyzed by water-soluble organometallic complexes; (2) design new water-soluble ligands for aqueous organometallic catalysis; (3) stabilize catalytically active noble metal nanoparticles in water; (4) facilitate reactions catalyzed by supported metals or metallic powder in water.

Chemically Modified Cyclodextrins: An Attractive Class of Supramolecular Hosts for the Development of Aqueous Biphasic Catalytic Processes

During these last years, cyclodextrins have contributed greatly to the development of catalytic processes in water. These cyclic oligosaccharides composed of 6(α), 7(β) or 8(γ) glucopyranose units improve the mass transfer in aqueous-organic two-phase systems and are useful compounds to design new catalysts. Thus, chemically modified cyclodextrins can be used to: (i) increase significantly the rate and selectivity of reactions catalyzed by water-soluble organometallic complexes, (ii) design new water-soluble ligands for aqueous organometallic catalysis, (iii) stabilize catalytically active noble metal nanoparticles in water and (iv) favour the dispersion and activation of the palladium on charcoal in water.

Evaluation of the catalytic activity of the water-soluble organometallic complex [Rh(μ-Pz)(CO)(TPPTS)] 2 in the hydroformylation of short-chain olefins in a refinery's naphtha cut

A water-soluble organometallic complex of rhodium, namely [Rh(μ-Pz)(CO)(TPPTS)] 2 [Pz = pyrazolate; TPPTS = P(C 6H 4SO 3Na) 3, tris(sodium- m-trisulphonated-triphenyl-phosphine)] was evaluated in the catalytic hydroformylation of the short-chain olefins contained in a naphtha cut from “El Palito” refinery in Venezuela. The reactions were carried under moderate conditions in an aqueous/organic biphasic medium. The naphtha current was characterized. Under the best reaction conditions (825 psi of syn-gas, T = 70 °C, S/C = 200:1) a very good conversion to aldehydes (96%) was obtained after 72 h. The mercury test was performed to the system proving that the reaction proceeds through molecular species. The recycling of the aqueous solution of the catalytic precursor was performed four times resulting in a decrease of activity from 96% to 60%.

Water-Soluble Organometallic Complexes of Tantalum: Can Alkyl and Aqua Ligands Coexist in Its Coordination Sphere?

The complexes [Cp*TaMe(OCH2)2py(H2O)]OTf (3), [Cp*Ta(OH)(OCH2)2py(H2O)]OTf (4), and [Cp*Ta(OCH2)2py(H2O)2]OTf2 (5) are described as the first examples of water-soluble organometallic derivatives of tantalum.

The pH dependent phase transfer of an organometallic complex: synthesis, characterization, and crystal structure of a W(0) tetracarbonyl with an acidic pyridine–imine ligand

Reaction of the asymmetrical pyridine–imine ligand L (where L=benzoic acid, 3-[(2-pyridinylmethylene)amino]) with W(CO) 3(EtCN) 3 and CO (g) affords a W(0) tetracarbonyl in which the Schiff-base ligand coordinates in a bidentate fashion. The complex was characterized by IR, NMR, and UV–visible spectroscopy and elemental analysis. The solid-state structure of W(CO) 4( L), which crystallized in the orthorhombic space group Pbca with unit cell parameters a=22.497(4) Å, b=14.112(6) Å, and c=13.675(3) Å was established by X-ray crystallography. Deprotonation of the –CO 2H group on the ligand with base results in the formation of a water-soluble organometallic complex which can be partitioned between organic and aqueous phases in a biphasic system by pH adjustment.

Some water-soluble organometallic complexes of group 10 transition metal (II) ions with 1,3,5-triaza-7-phosphaadamantane (TPA) . Syntheses, characterization and reactivity. The crystal and molecular structure of [Ni (CN) 2 (TPA) 3] · 4.3H 2O

The 1,3,5-triaza-7-phosphaadamantane [TPA] complexes of the type [MCl 2 (TPA) 2] (where M = Ni, Pd, Pt) , [Ni (CN) 2 (TPA) 3] and [PtCl (TPA) 3] (BPh 4) have been synthesized and characterized by 1H, 31P { 1H} NMR, Laser-Raman spectroscopy and elemental analyses. The reactivity of the complexes [MCl 2 (TPA) 2] with water to produce the oxide of TPA follows the order Pt > Pd > Ni. The structure of the complex [Ni (CN) 2 (TPA) 3] · 4.3H 2O was determined by single crystal X-ray diffraction methods. The structure determination shows that the nickel atom has a trigonal-bipyramidal geometry with the cyanide ligands in the apical positions.

Comparative study of C(2) epimerization of d-glucose and d-mannose catalyzed by water soluble organometallic complexes with nitrogen ligands

Epimerization of d-glucose and d-mannose, catalyzed by the water soluble complexes of Cu(II), Ni(II), Co(II) and Cd(II) with bisnitrogen ligands 4–7, and by Mo(VI) complexes prepared in situ from ammonium heptamolybdate (AHM) with ligands 4–9 is compared. All examined complexes exhibit lower catalytic activity than AHM: strong coordination of the ligands by both (N,O) heteroatoms to metal ions, presumably affords catalytically less active species. Some free ligands and their metal (II) complexes catalyze both C(2) epimerization and isomerization of aldoses to d-fructose.

Enhancement of interfacial catalysis in a biphasic system using catalyst-binding ligands

TO avoid the problem of separation of products from catalyst in homogeneous catalysis1, two-phase systems have been developed in which the catalytic complex (usually a water-soluble organo-metallic complex) remains in one (generally aqueous) phase while the products remain in a second, immiscible phase2. Catalysis relies on the transfer of organic substrates into the aqueous catalyst phase; but the limited solubility of these substrates in water leads to reaction rates much lower than those for conventional homo-geneous catalysis. Here we show that catalysis at the interface of a two-phase system can be enhanced by using a 'promoter ligand' which, although soluble in the organic phase, will bind to the organometallic catalyst and thus increase its concentration close to the interface in the aqueous phase. We demonstrate this approach for the hydroformylation of 1-octene using a rhodium-based catalyst. A rate enhancement by a factor of 10–50 is observed when we introduce the promoter ligand PPh3 in the organic phase.

Catalysts span aqueous, organic phase gap

The search for new catalysts follows many different paths. One of the more intriguing new approaches to catalysis is the development of catalysts that bridge the gap between aqueous and organic phases that are normally active only at their interfaces. A number of catalysts are operative only in aqueous solution, but have potential applications in petrochemistry. Work aimed at reconciling the usual intractabilities has begun. Mark E. Davis, a chemical engineering professor at California Institute of Technology, has developed a new immobilization method designed to convert liquid-phase reactants. At a session of the Division of Industrial & Engineering Chemistry, he described the catalysts as supported-aqueous-phase (SAP) catalysts, consisting of thin films that reside on high-surface-area hydrophilic supports. The film is composed of watersoluble organometallic complexes and water. Reactions of liquid-phase waterinsoluble organics take place at the filmorganic interface. SAP catalysts are distinguished fro...

Supported aqueous-phase catalysts

This work describes a novel family of catalysts denoted supported aqueous-phase catalysts. These catalysts consist of a water-soluble organometallic complex supported in a thin film of water residing on a high-surface-area hydrophilic solid. The catalytic reaction takes place at the water-organic interface where the organic phase contains the reactants and products. Supported aqueous-phase catalysis is demonstrated by liquid-phase hydroformylation. The solid support used here was either CPG-240 or CPG-350; both are porous glasses with narrow pore volume distributions. The catalytic species, HRh(CO)[ m-P(PhS0 3Na) 3] 3 was synthesized from Rh(CO) 2(acac) by a new synthetic route and impregnated onto CPG-240. Solution and solid-state 31P NMR data are consistent with a mobile rhodium species in the aqueous phase in hydrated forms of the catalyst. The hydroformylation of oleyl alcohol (OLOH) was accomplished at 100°C and 5.1 MPa of H 2/CO (1/1) using 0.002 g Rh/g OLOH. For example, conversions of up to 96.6% could be achieved in 5.5 h. It is postulated that no significant leaching of Rh occurs, since after filtration to remove the solid catalyst the remaining solution showed no activity for either the hydroformylation of additional OLOH or the hydrogenation of added 1-hexene. The observations that (1) OLOH and its hydroformylation products are not water soluble, (2) the double bond of OLOH is internal, and (3) the Rh does not leach into the organic phase demonstrate the concept of SAP catalysis; the immobilized homogeneous catalyst is active at the interface of two immiscible phases.

ChemInform Abstract: Hydroformylation by Supported Aqueous‐Phase Catalysis: A New Class of Heterogeneous Catalysts.

HOMOGENEOUS catalysts typically operate at relatively mild temperatures and exhibit high activities and selectivities1. However, it has long been recognized that many homogeneous reactions are not commercially viable because of problems of catalyst recovery. Thus, significant efforts have centred around the immobilization of the organometallic species responsible for catalysis2. At best, the performance of such heterogeneous catalysts only approximate those of their homogeneous counterparts. Here we describe a novel family of heterogeneous catalysts, denoted supported aqueousphase catalysts (SAPCs), designed to facilitate chemical reactions at the interface of two liquids. These catalysts consist of a watersoluble organometallic complex dissolved in a film of water which is supported on a high-surface-area hydrophilic solid. Reactions of liquid-phase organic reactants take place at the water–organic interface. Heterogeneous hydroformylation of alkenes by SAPCs containing water-soluble organometallic rhodium complexes is used to illustrate the efficacy of these new catalysts.

Hydroformylation by supported aqueous-phase catalysis: a new class of heterogeneous catalysts

HOMOGENEOUS catalysts typically operate at relatively mild temperatures and exhibit high activities and selectivities1. However, it has long been recognized that many homogeneous reactions are not commercially viable because of problems of catalyst recovery. Thus, significant efforts have centred around the immobilization of the organometallic species responsible for catalysis2. At best, the performance of such heterogeneous catalysts only approximate those of their homogeneous counterparts. Here we describe a novel family of heterogeneous catalysts, denoted supported aqueousphase catalysts (SAPCs), designed to facilitate chemical reactions at the interface of two liquids. These catalysts consist of a watersoluble organometallic complex dissolved in a film of water which is supported on a high-surface-area hydrophilic solid. Reactions of liquid-phase organic reactants take place at the water–organic interface. Heterogeneous hydroformylation of alkenes by SAPCs containing water-soluble organometallic rhodium complexes is used to illustrate the efficacy of these new catalysts.