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A study to examine the catalytic properties of small clusters of rhodium and of iridium on oxide supports using the hydrogenation reaction of ethene, propene, and toluene was conducted. The results indicated self-inhibition of reaction adsorbed hydrocarbons and differences between ethene hydrogenation and propene hydrogenation that may arise primarily from different adsorbate-adsorbate interactions.

Iridium catalyzed alcohol C-C coupling is used to perform total synthesis of the oxo-polyene macrolide (+)-roxaticin in 20 steps from 1,3-propanediol. The reaction representing the simplest synthesis of any oxo-polyene macrolide could be achieved in the absence of chiral reagents and chiral auxiliaries with minimal use of premetalated C-nucleophiles.

A highly efficient and enantioselective hydrogenation method to catalyze unprotected [beta]-enamine esters in presence of Ir-(S,S)-f-binaphane complex is described. The developed methodology provides straightforward access to free [beta]-amino acids in high yield with excellent enantioselectivities up to 97% ee and high reactivities of more than 5000 TON.

The article explains the various mechanisms and applications of the different Ir-catalyzed intramolecular allylic alkylation reactions. These reactions are shown to be extremely beneficial for the synthesis of spiroindolenines.

The article presents a new approach, which can be employed for the one-pot meta cyanation of different arenes by using the iridium-catalyzed borylation of the esters. The various mechanisms involved and the utility of the method are also analyzed.

The ortho-cyclometalated [pi]-allyl iridium was used as precatalyst to synthesize products of (trimethylsilyl)allylation with exceptional levels of anti-diastereoselectivity and enantioselectivity in the presence of aldehydes and mediated by 2-propanol. The carbonyl (trimethylsilyl)allylation could also be achieved directly from the alcohol oxidation level to deliver an equivalent set of adducts (trimethylsilyl)allylation with roughly equivalent isolated yields and stereoselectivities in the absence of 2-propanol.

Versatile methods for iridium-catalyzed, kinetic asymmetric substitution of racemic, branched allylic esters are reported. The kinetic asymmetric reaction processes occur with distinct stereochemical courses for racemic aliphatic and aromatic allylic benzoates and the high reactivity of branched allylic benzoates facilitates enantioselective allylic substitutions that are slow or poorly selective with linear allylic electrophiles.

A nucleophilic substitution of propargylic alcohols with carbon, sulfur, oxygen and nitrogen nucleophiles is shown by using a high-valent [[Ir(COD)(Sn[Cl.sub.3])Cl([mu]-Cl)].sub.2] catalyst in 1,2-dichloroethane to produce the corresponding propargylic products. Alkyl or aryl substituted tertiary propargylic alcohols have produced substituted indenes with bulky arenes through allenylic intermediate and an electrophilic mechanism is described from Hammett correlation.

Iridium-catalyzed asymmetric 1,6-addition of arylboroxines to [alpha],[beta],[gamma],[delta]-unsaturated carbonyl compounds is reported. The reaction gave [delta]-arylated carbonyl compounds in high yields with 90 to 99% enantioselectivity realized by use of an iridium/chiral diene complex.

The ester-directed regioselective borylation of arenes catalyzed by a silica-supported monophosphine-Ir complex has exhibited a broad substrate scope toward heteroaromatic compounds, including thiophene, pyrrole, furan, benzothiophene, benzofuran, indole, and carbazole derivatives. The regioselectivity is complementary to the selectivities in the heteroarene C-H borylation with the dtbpy-Ir catalyst system.

Hydrogenation of the (PONOP)Ir(I)C[H.sub.3] complex [PONOP = 2,6-bis(di-tert-butylphosphinito)pyridine] has produced the trans-dihydride species (PONOP)IrC[H.sub.3][(H).sub.2]. Protonation has produced the cationic (PONOP)Ir(C[H.sub.3])[(H).sup.+] complex, which is then trapped by [H.sub.2] to produce an [[eta].sup.2]-[H.sub.2] complex, whereas deprotonation of this species has produced the trans-dihydride.

Iridium(III)-salen complexes have efficiently catalyzed enantioselective carbene Si-H bond insertion. The formation of a chiral silicon center is achieved by the Si-H insertion into prochiral silanes, where the reactions between prochiral silanes and tert-butyl [alpha]-diazopropionate in the presence of {(aR,S), Ar = Ph} has proceeded with high stereoselectivity.

The preparation of [omega]-hydroxy carboxylic acids and [alpha],[omega]-dimethyl diketones is achieved by using [alpha],[omega]-diols as alkylating agents under the affect of an iridium catalyst. The alkylation of acetone with 1,10-decanediol in the presence of [[IrCl(cod)].sub.2] and KOH has resulted in a muscone precursor, 2,15-hexadecanedione (HDDO).

5-Substituted-2-furan methanols are subjected to enantioselective carbonyl allylation, crotylation and tert-prenylation after exposing to allyl acetate, [alpha]-methyl allyl acetate, or 1,1-dimethylallene in the presence of an ortho-cyclometalated iridium catalyst modified by (R)-Cl,MeO-BIPHEP, (R)-C3-TUNEPHOS and (R)-C3-SEGPHOS. Optically enriched products of carbonyl allylation, crotylation and reverse prenylation are subjected to Achmatowicz rearrangement for producing the corresponding [gamma]-hydroxy-[beta]-pyrones, with negligible erosion of enantiomeric excess.

A complex of [[Ir(OMe)(cod)].sub.2] and 4,4-di-tert-butyl-2,2-bipyridine (dtbpy) has catalyzed the Z-selective, dehydrative silylation of terminal alkenes, but not 1,2-disubstituted alkenes, with triethylsilane or benzyldimethylsilane in THF. Yields and Z-stereoselectivity are improved by 2-norbornene, whereas [alpha],[beta]-unsaturated esters are unreactive and the reaction has proceeded through a Heck-type mechanism.

The application of heterodinuclear iridium-ruthenium complex as the most efficient catalyst for selective production of hydrogen from formic acid in an aqueous solution at ambient temperature is reported. The catalytic hydrogen production in [H.sub.2]O vs [D.sub.2]O is observed to show an unusually large tunneling effect for the first time.

The mechanisms involved in the iridium-catalyzed highly enantioselective hydrogenation of [alpha]-aryloxy and [alpha]-alkoxy [alpha],[beta]-unsaturated carboxylic acids are explained. The catalyst is shown to lead to an excellent chiral discrimination because of the presence of a completely hindered chiral environment.

Several studies are conducted to determine the applicability of the [[Ir(COD)Cl].sub.2] compound for catalyzing the intramolecular hydroamination of unactivated alkenes with primary amines and secondary alkyl- or arylamines.

The real-time characterization of changes in the structure of a catalyst at the molecular level is described along with reversible interconversion of mononuclear iridium complexes and tetrairidium clusters inside zeolite Y cages, with the structure controlled by the [C.sub.2][H.sub.4]/[H.sub.2] ratio during ethene hydrogenation The evidence confirming the structural change is given by infrared (IR) spectra of iridium carbonyls formed by studying the catalyst with CO.

A dissolved electroactive nanoparticle is used for describing the redox catalysis, which is based on the oxidation of water by electrogenerated Ir[O.sub.x] nanoparticles containing [Ir.sup.VI] states, in pH 13 solutions of [Ir.sup.IV][O.sub.x] nanoparticles capped by hydroxide. Controlled potential coulometry has shown that all Ir sites in the nanoparticles are electroactive and both the overpotential and turnover (TO) values are nearly the same as observed for films electroflocculated from similar Ir[O.sub.x] nanoparticles.

The complete characterization of a series of three iridium/palladium heterometallic complexes prepared from the ligand 1,2,4-trimethyl-triazolyl-diylidene are reported. The combined reactions that are typically catalyzed by Ir and Pd could be used to design tandem processes in presence of two different metals.

The ability of iridium(III)-salen complexes to efficiently catalyze the enantioselective C-H carbene insertion is demonstrated. An appropriate combination of complexes in the reaction and [alpha]-diazoacetate ([alpha]-aryl-[alpha]-diazoacetates or [alpha]-diazopropionate) as the carbene source is found to achieve the insertion reaction at the [alpha]-position of tetrahydrofuran or at the methylene of 1,4-cyclohexadiene proceeded with high enantio- and diastereoselectivity (up to 99%).

A newly synthesized isopropyl-substituted PNP-pincer iridium trihydride complex as a catalyst is used to perform catalytic hydrogenation of carbon dioxide in aqueous potassium hydroxide. The turnover of obtained potassium formate is found to be the highest values reported to date.

A modular library of phosphite-oxazoline ligands is applied in the Ir-catalyzed asymmetric hydrogenation of a broad range of highly unfunctionalized 1,1-disubstituted terminal alkenes. The asymmetric hydrogenations are performed by using propylene carbonate as solvent, which has allowed the Ir catalyst to be reused and maintained the excellent enantioselectivities.

The various mechanisms involved in the highly enantioselective, iridium-catalyzed monoallylations of ammonia are explained. The methodology is shown to be extremely useful for the one-pot syntheses of heterodiallylamines and allylic amides.

Oxidative addition of bulky primary, secondary, and tertiary silanes to PNP (where PNP = [N[(2-[P.sup.i][Pr.sub.2]-4-Me-[C.sub.6][H.sub.3]).sub.2]](-)) iridium complexes (PNP)Ir[H.sub.2] and (PNP)Ir(COE) (11) which afforded iridium silyl hydride complexes (PNP)Ir(H)(SiRR?R??) are described. The structurally characterized Ir(V) disilyl PNP complex was found to be catalytically active for the hydrosilation of alkenes which is consistent with its intermediacy in the catalytic cycle.

Highly regio- and enantioselective iridium-catalyzed N-allylations of benzimidazoles, imidazoles and purines are developed in the presence of single component, ethylene-bound, metallacyclic iridium catalysts. The studies have helped in the development of N-allylations of benzimidazoles and imidazoles in the absence of an exogeneous base.

Iridium complexes with novel N,P-chelating ligands are applied to the asymmetric hydrogenation of trisubstituted olefins, which has formed diarylmethine chiral centers in high conversions and excellent enantioselectivities (ee) for a broad range of substrates. The results have shown that excellent stereodiscrimination is obtained even when the prochiral carbon bore phenyl and p-toyly groups.

The studies have shown that a series of Cp*Ir catalysts are the most active known by over an order of magnitude for water oxidation with Ce(IV). Density functional theory calculations have supported a Cp*Ir[double bond]O complex as an active species.

The homogeneous catalytic system for the efficient reversible dehydrogenation-hydrogenation reactions of nitrogen heterocycles in one flask is developed by using the pyridonate Cp*Ir complex as the single catalyst at relatively low temperature. The feature of the present homogeneous catalytic system is that the reversible dehydrogenation-hydrogenation reactions have proceeded with the reversible interconversion of the catalytic species, depending on the absence or presence of hydrogen.

Iridium complex derived from [[Ir(COD)Cl].sub.2]/Feringas ligand is an efficient catalytic system for the cross-coupling reaction between allyl carbonates and o-amino styrene derivatives, which has afforded skipped Z, E dienes. The reaction has featured the availability of the starting materials, mild reaction conditions, high yields and excellent stereoselectivity.

Iridium-catalyzed asymmetric hydrogenations via the use of substrates like diphenylvinylphosphine oxides and di- and trisubstituted vinylphosphonates is demonstrated. The hydrogenated products obtained for both aromatic and aliphatic groups of substrates could find application as synthetically useful intermediates.

Direct reductive amination of a wide range of ketones is accomplished by the cooperative catalysis of an Ir(III)-diamine complex and a chiral phosphoric acid or its conjugate base.

An immobilized monophosphine-Ir system is prepared from [[Ir(OMe)(cod)].sub.2] and a silica-supported, compact phosphine and it has shown high activities and selectivities for the borylation of aromatic C-H bonds with bis(pinacolato)diboron. This system is effective for the borylation of benzene and also for the ortho borylation of arenes with directing groups, such as ester, amide, sulfonate, acetal, alkoxymethyl, and chloro groups, under mild reaction conditions.

The acid-catalyzed hydrogenation of ketones by amido-amine chelates of Ru and Ir are examined by focusing on the hydrogen activation step. The addition of [H.sub.2] to the catalyst Cp*Ir (TsDPEN-H) (TsDPEN = racemic [H.sub.2]NCHPhCHPhN[Ts.sup.-]) is more favorable than for corresponding (cymene)Ru derivatives.

The experiments aimed at probing the origins of stereoselection have established a matched mode of ionization for the (R)-acetate and the iridium catalyst modified by (S)-SEGPHOS, as well as reversible ionization of the allylic acetate with rapid [pi]-facial interconversion of the resulting [pi]-crotyl intermediate in advance of C-C bond formation. anti-Diastereo- and enantioselective carbonyl crotylation from the alcohol or aldehyde oxidation level is obtained in the absence of any stoichiometric metallic reagents or stoichiometric metallic byproducts.

A combination of an iridium-catalyzed C-H activation/borylation and the Suzuki-Miyaura reaction is used to develop a new synthetic method for the introduction of functional groups into polysulfone. A new family of functionalized polysulfones prepared from highly efficient and mild postfunctionalization method could find wide application in new high-performance engineering plastic materials.

The highly enantioselective hydrogenation of cyclic N,N-dialkyl enamines by using chiral iridium complexes of spiro phosphoramidites and it application in the synthesis of optically active cyclic tertiary amines, including the natural product crispine A is described. The asymmetric hydrogenation of enamine is performed under the optimized conditions by using the iridium catalyst to produce crispine A in 97% yield.

The cationic iridium pincer catalysts are used for the room-temperature cleavage and reduction of a broad range of alkyl ethers with triethylsilane. The catalyst resting states, isolation and spectroscopic and structural characterization of a key intermediate, the diethyl(triethylsilyl)oxonium ion, in the reduction of diethyl ether are presented.

The isolation and characterization of both an Ir-enol tautomer intermediate and an Ir-keto tautomer intermediate in the catalytic hydration by optimizing the conditions of the isolation, such as pH of the solution, reaction time and selection of counteranions, are described. The mechanism of the catalytic hydration of tetrolic acid ethyl ester as an alkyne-carboxylic ester is described that is based on isotopic labeling experiments with the Ir-enol and Ir-keto tautomers.

A novel catalytic system is described for the aerobic oxidation of primary and secondary alcohols. A new mechanism is presented for the Ir-catalyzed aerobic oxidation that has shown that the transition metal has maintained its (+3) oxidation state throughout the entire catalytic cycle.

The studies have shown that when combined with a chiral phosphate anion, diamine-ligated Ir(III) catalysts have enabled highly enantioselective asymmetric hydrogenation of acyclic imines. The catalyst is viable for a wide range of imines and might operate via cooperative catalysis between a chiral metal catalyst and its chiral counteranion.

The application of iridium complex ([[kappa].sup.3]1,3-[(OP[super t][Bu.sub.2]).sub.2][C.sub.6][H.sub.3]Ir[(H).sub.2] as an efficient catalyst for the rapid dehydrogenation of amine boranes (MeAB) and AB/MeAB mixtures is reported. The reaction yields soluble oligomers and copolymers and provides insight into the kinetic and thermodynamics of reaction materials for hydrogen storage.

The application of the concepts in hydrogenations mediated by complexes for producing the internal and terminal chirons A and B found in many natural products and useful derivatives is described. The constructive matching of chiral Crabtree's catalyst analogues with stereochemical vectors from substrates has produced high diastereoselectivities.

The highly enantioselective Ir-catalyzed hydrogenation of [alpha],[beta]-unsaturated carboxylic acids is developed by using spiro iridium/phosphine-oxazoline (SIPHOX) ligands. The extremely high activity, enantioselectivity and mild reaction conditions have shown that the Ir-SIPHOX is excellent catalysts for preparing enantiopure carboxylic acids.

A novel approach based on hydrosilanes as directing groups was used to perform iridium-catalyzed ortho-borylation of arenes. The method can be used to develop regioselective functionalization of benzylic silanes, phenols, and anilines.

The first successful application of phosphite containing ligands in the Ir-catalyzed asymmetric hydrogenation of several unfunctionalized olefins is described. The easily prepared new class of phosphite-oxazoline ligands provides higher enantioselectivities compared to phosphinite-oxazoline analogue.