Search

The emission λmax are strikingly shorter (451, 482 nm) for the cationic dicarbonyl complex [Ir(ppy)2(CO)2]+ (2a) than those (473, 495 nm) of the anionic dicyano complex [Ir(ppy)2(CN)2]–, where CO and CN– are both sp carbon coordinating ligands and known to be strong-field ligands showing a high trans effect. Sky-blue-light emission (λmax = 441–443 and 470–471 nm) could be obtained by modifying the ppy ligand to F2Meppy (2,4-difluoro-2-phenyl-m-methylpyridinato anion) to prepare [Ir(F2Meppy)2LL′]+ [LL′ = (CO)2 (2aF2Me), (PPh2Me)2 (2bF2Me)]. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)

A new type of iridium(III) complex [trans-Ir(ppy)2(PPh3)2]+ (1) has been prepared by a novel synthetic method and its structural and photoluminescent characteristics have been compared with those of the cis analogue, [cis-Ir(ppy)2(PPh3)(P(OPh)3)]+ (2) which has also been newly prepared in this study. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)

Cationic iridium complex [Ir(CH 3 )(OTf)(CO)(OH 2 )(PPh 3 ) 2 ](OTf) ( 1 ) catalyzes addition of diols (HO (CH 2 ) n OH ( n = 2–6)) to terminal alkynes (RC CH: R H, CH 2 (CH 2 ) 2 CH 3 , C 6 H 5 , p -CH 3 C 6 H 4 ) to produce cyclic acetals exclusively in the absence of H 2 O at room temperature. While complex 1 does not catalyze the hydration of alkynes to produce the carbonyl compounds (RCOCH 3 ), the cyclic acetals rapidly undergo hydrolysis to give RCOCH 3 and regenerate diols in the presence of 1 . A deuterium-labeling study (MeO D + n- BuC CH → CH D 2 C(OMe) 2 ( n -Bu)) suggests a reaction pathway involving a π-alkyne complex, η 2 -(RC CH)Ir which is attacked by alcohol (R′O D ) to give a β-alkoxy-alkenyl complex, Ir CH CRO + D R′. Proton transfer and attack by another alcohol molecule on the intermediate, Ir CH D C + R(OR′) to produce Ir CH D CR(OR′) O + D R′ that finally yields the acetal CH D 2 CR(OR′) 2 . It has been found that bulky substituents R on RC CH cause a decrease in the rate of diol addition, and that the production of six- and seven-membered acetals is faster than that of five- and eight-membered ones.

In this account we summarize our recent works on the synthesis of iridium-unsaturated hydrocarbyls that contain metal–carbon σ-bonds and their reactions to produce unsaturated organic compounds regio- and stereospecifically. Iridium–carbon σ-bonds are made during the formation of iridium complexes such as metal-alkynyls, -alkenyls, -carbenes (vinylidenes), -alkyls and carbonyls from reactions of terminal alkynes with iridium. The β-carbon of alkynyl ligand is in general so nucleophilic that it is readily attacked by electrophiles to make the α-carbon of the alkynyl ligand reactive with the nucleophilic carbon of the neighboring hydrocarbyl ligand to form new C–C bonds between hydrocarbyl ligands. These C–C bond forming reactions selectively produce interesting unsaturated organic compounds such as conjugated polyenes, polyene-ynes, cross-conjugated polyenes and cis-olefins. To cite this article: C. S. Chin, H. Lee, C. R. Chimie 8 (2005).

Iridabenzenes are produced by an unusual C−C coupling between the α-carbon of the alkynyl ligand and the δ-carbon of the neighboring 1,3-butadienyl ligand upon protonation of the β-carbon of the al...

Alkyl-carbonyl-iridium [Ir(CH3)(CO)(η2-O2CR′)(PPh3)2]+ (1, R′ = CH3, Ph, p-C6H4CH3) react with alkynes (RC CH; R = Ph, p-C6H4CH3) in the presence of NEt3 to give acyl-alkynyl-iridium Ir(C( O)CH3)(–C CR)(η2-O2CR′)(PPh3)2 (4) which further react with RC CH to give alkyl-carbonyl-cis-bis(alkynyl) iridium Ir(CH3)(CO)(C CR)2(PPh3)2 (5). cis-Bis(alkenyl)iridium complexes, Ir(–CH CH2)2(η2-O2CCH3)(PPh3)2 (6) and (η2-O2CCH3)(PPh3)2 (7) react with substituted alkynes RC CH (R = Ph, p-C6H4CH3, cyclohex-1-enyl) to give cis-bis(alkynyl) Ir(C CR)2(η2-O2CCH3)(PPh3)2 (9) that further react with RC CH to undergo the alkyne insertion reaction into the Ir–O bond to produce iridacycles containing vinyl acetate ligands, (–C CR)2(PPh3)2 (8).

Silicon nanocrystals in a range from 2 nm to 5 nm were prepared from Zintl salt, soldium silicide (NaSi) by sonochemical method. This synthesis permits that the reaction be completed in only a few hours and the easy alkyl-modification of nanocrystals surface at room temperature and ambient pressure. The average size of nanocrystals measured by the dynamic light scattering analysis was 2.7 nm. The high-resolution transmission electron micrograph confirmed the material identity of nanocrystals as crystalline silicon. FT-IR spectra are consistent with the surface states of nanocrystals that are chlorine-or butyl-capped. The emission peak center moved to a longer wavelength (up to 430 nm) with the reaction time, under a 325 nm excitation.

The second generation of Grubbs type catalyst, (PCy3)(H2IMes)Cl2Ru CHPh (1) undergoes the Cl replacement with CH3CN to give cationic ruthenium carbene complexes, [(RCN)3(H2IMes)Ru CHPh](OTf)2 (2, R = CH3 (a), Ph (b)) in the presence of AgOTf. The reaction of 2a with H2O in the presence of CH3CN gives (aqua)ruthenium complex, [Ru(H2IMes)(NCCH3) 4(H2O)](OTf)2 (3) and benzaldehyde. Benzaldehyde is also observed in the reaction of 1 with H2O. Plausible reaction pathways are suggested for the degradation of ruthenium benzylidenes to give benzaldehyde on the basis of the isotope labeling experiments.

Phosphorus–carbon bond is formed via: (i) the apparent HCCH insertion into Ir–P bond to produce Ir–CHCH–PPh3 group and (ii) the activation of the ring-methyl group of the coordinated Cp* (C5Me5 −) to produce Ir(η5-C5Me4CH2–PPh3) group from reactions of iridium(III)–Cp* complexes, [Cp*IrL3]n+ (n=1, 2); Cp*=C5Me5 −; L3=Cl(PPh3)2 (3), (CH3CN)3 (5). The following new P–C bond containing iridium(III) complexes have been prepared: [Cp*Ir(–CHCH–PPh3)Cl(PPh3)]+ (4) from 3 with HCCH; [Ir(η5-C5Me4CH2–PPh3)(H)(PPh3)2]2+ (6) from 5 with PPh3; [Cp*Ir(–CHCH–PPh3)2(PPh3)]2+ (7) from 5 with HCCH and PPh3; [Ir(η5-C5Me4CH2–PPh3)(–CHCH–PPh3)Cl(PPh3)]2+ (8) from [Ir(η5-C5Me4CH2–PPh3)(Cl)(PPh3)2]2+ (6-Cl) with HCCH; [Ir(η5-C5Me3(1,3-CH2–PPh3)2(H)(PPh3)2)]3+ (10) from [Ir(η5-C5Me4CH2–PPh3)(NCCH3)2(PPh3)]3+ (9) with PPh3; [Ir(η5-C5Me4CH2–PPh3)(–CHCH–PPh3)2(PPh3)]3+ (11) from 9 with HCCH and PPh3.

Acyliridium-alkoxycarbenes [Ir(C(OR‘)CH3)(C(O)R)(η2-O2CCH3)(PPh3)2]OTf (3, R = CH3, R‘ = CH3 (a), R = CH3, R‘ = CH2CH3 (b), R = CH2Ph, R‘ = CH3 (c), R = CH2Ph, R‘ = CH2CH3 (d)) and (4, R = CH3) are obtained from reactions of [Ir(R)(η2-O2CCH3)(CO)(PPh3)2]OTf (2, R = CH3 (a), CH2Ph (b)) with HC⋮CH/R‘OH and HC⋮CCH2CH2OH, respectively. Complex 2a also undergoes 1,1-insertion reaction of HC⋮CH into an Ir−O bond to give an iridacycle containing a vinyl acetate (−C(CH2)OC(CH3)O−) ligand, (5), in the absence of an alcohol. The methyl group of the alkoxycarbene ligand of 3a is readily transferred to the central metal to give a methyliridium complex and also by PPh3 in solution to give a bis-acyliridium complex. Plausible reaction pathways are suggested for the formation of acyliridium-alkoxycarbenes and the iridacycle containing a vinyl acetate (−C(CH2)OC(CH3)O−) ligand on the basis of the deuterium labeling experiments.

The reactions of KSeO2(OCH3) (1) in methanol with [Rmim]Cl (Rmim = 1-alkyl-3-methylimidazolium) at room temperature give imidazolium-based ionic liquids containing methylselenite anion, [Rmim][SeO2...

A carbon−carbon bond is formed between the α-carbons of the alkenyl ligands of the cis-bis(ethenyl)iridium complex [Ir(−CHCH2)2(CH3CN)2(PPh3)2]+ (2) to produce the η3-allyl complex [Ir(η3-CH3CHCHCH2)(NCCH3)2(PPh3)2]2+ (4) in the reaction of 2 with H+, and η4-butadiene complexes Ir(η4-CH2CHCHCH2)(A)(PPh3)2 (A = −CHCH-+NEt3 (6), −C⋮CR (7)) in reactions of 2 with terminal alkynes (RC⋮CH; R = H, Ph, and p-C6H4CH3) in the presence of NEt3. The deuterium labeling experiments suggest an initial attack of H+ on the β-carbon of an ethenyl ligand to lead to the C−C bond formation between the α-carbons of the two alkenyl groups of 2 to produce 4.

cis,cis-1,4-Dipropenylbenzene (cis,cis-p-C6H4(CHCHCH3)2, cis-DPB) and cis,cis,cis-1,3,5-tripropenylbenzene (cis,cis,cis-m,m-C6H3(CHCHCH3)3, cis-TPB) are obtained in high yields by reactions of di- and tri-nuclear alkyl–alkenyl–alkynyl iridium(III) compounds, [p-C6H4(CC–Ir(CH3)(CHCHPPh3)(CO)(PPh3)2)2]2+1 and [m,m-C6H3(CC–Ir(CH3)(CHCHPPh3)(CO)(PPh3)2)3]3+3 with HCl. The reaction of the mono-nuclear alkyl–alkenyl–alkynyl iridium(III) complex, [Ir(CH3)(CHCHPPh3)(CC-p-C6H4CH3)(CO)(PPh3)2]+7a with DCl selectively gives cis-CD3CDCD(p-C6H4CH3) 8a-d5 while two isomers, cis-C6H5CD2CDCD(p-C6H4CH3) 8b-d4 and cis-C6H5CDCDCD2(p-C6H4CH3) 8b′-d4 are obtained from the reaction of [Ir(CH2Ph)(CHCHPPh3)(CC-p-C6H4CH3)(CO)(PPh3)2]+7b with DCl. Plausible reaction pathways containing the initial attack of H+ on the β-carbon of the alkynyl ligands to produce cis-alkenyl complexes that give η2-allene complexes are suggested for the selective and diastereocontrolled C–C bond forming reactions between alkyl and alkynyl groups to give cis-olefins, 8, cis-DPB, and cis-TPB.

Reactions of the iridacyclopentadienes (2a) and (2b) with RC⋮CH (R = C6H5, p-C6H4CH3) give linear conjugated dienynes (RC⋮CCHCHCHCH2 (3) and (5)) and benzene derivatives (RC6H5 (4) and RC6H3C6H8 (6, 6-aryl-1,2,3,4-tetrahydronaphthalene)). Linear conjugated dienynes 3 and 5 are exclusively obtained from the reactions of alkynyl iridacyclopentadienes (7) and (8) (R = C6H5 (a), p-C6H4CH3 (b), cyclohex-1-enyl (c)) with HOTf, respectively. The di- and trinuclear alkynyl iridacyclopentadienes (9a), (9b), and (10) (L3 = (CO)(PPh3)2) react with HOTf to produce the extended and conjugated dienynes p-C6H4(C⋮CCHCHCHCH2)2 (11), (12), and m,m-C6H3(C⋮CCHCHCHCH2)3 (13), respectively, in high yields. Iridacyclohexadienes (17, R‘ = H (a), CH3 (b)) are obtained from the reactions of 7 with HBF4 through a C−C bond-forming reaction between the α-carbons of alkynyl and 1,3-butadiene-1,4-diyl ligands. Plausible reaction pathways are suggested for the C−C bond-forming reaction between RC⋮CH and 1,3-butadiene-1,4-diyl ligands of...

Reactions of cis-dihydrido complex [Ir(H)2(NCCH3)2(PPh3)2]+ (1) with HC⋮CH and RC⋮CH (R = C6H5, p-C6H4CH3, cyclohex-1-enyl, C(CH3)CH2, C(CH3)3) produce cross-conjugated hexatrienes (RCHC(CHCH2)2, R-HEX) and octatetraenes (H2CCH−CRCH−C(−CHCH2)CHR, R2-OCT). Two molecules of HC⋮CH are inserted into Ir−H bonds of 1 to give cis-bis(ethenyl) complex [Ir(CHCH2)2(NCCH3)2(PPh3)2]+ (2), which reacts with RC⋮CD to produce both R-HEX-d1 (RCDC(CHCH2)2) and R2-OCT-d2 (H2CCH−CRCD−C(−CHCH2)CDR). R-HEX are exclusively obtained from the reactions of RC⋮CH with [Ir(CHCH2)2(CO)2(PPh3)2]+ (3). Alkynyl cis-bis(ethenyl) complexes Ir(CHCH2)2(C⋮CR)(CO)(PPh3)2 (4, R = C6H5 (a), p-C6H4CH3 (b), cyclohex-1-enyl (c)) react with D+ to give η4-R-HEX-d1 complexes [Ir(η4-RCDC(CHCH2)2)(CO)(PPh3)2]+ (5-d1) from which R-HEX-d1 are obtained in the presence of a base. Di- and trinuclear alkynyl−bis(alkenyl) complexes [L5Ir−C⋮C-p-C6H4-C⋮C−IrL5] (7, L5 = (−CHCH2)2(CO)(PPh3)2) and [L5Ir−C⋮C-m,m-C6H3-(C⋮C−IrL5)2] (8, L5 = (−CHCH2)2(CO)(PPh3)2) rea...

Reactions of water-soluble Cp*IrCl2(PAr3) (1) with alkynes HC⋮CR in H2O/C6H6 give new water-soluble alkyl-carbonyl complexes, [Cp*Ir(−CH2R)(CO)(PAr3)]+ (2, R = Ph (a), CH2Ph (b), C(CH3)3 (c), p-C6H4CH3 (d)) by cleaving the C⋮C bond of the alkynes. The CC bond of ethylene is also cleaved in the reaction of complex 1 with ethylene in the presence of Ag+ in water to give [Cp*Ir(−CH3)(CO)(PAr3)]+ (3).

Iridium complexes containing four Ir-C σ-bonds, cis,cis-[Ir(CH 3 )(-CH=CHPPh 3 )2(-C≡ CR)(PPh 3 ) 2 ] + (2, R = p-C 6 H 4 CH 3 (a), cyclohex-1-enyl (b), C(CH 3 )=CH 2 (c)), are obtained from the reactions of cis,trans-[Ir(CH 3 )(-CH=CHPPh 3 ) 2 (CO)(PPh 3 ) 2 ] 2 - (1) with HC≡CR in the presence of Me 3 NO. One of the two PPh 3 in 2 is readily replaced to give complexes containing five Ir-C σ-bonds, cis-[Ir(CO)(CH 3 )(-CH=CHPPh 3 ) 2 (-C≡CR)(PPh 3 )] + (3, R = p-C 6 H 4 CH 3 (a), cyclohex-1-enyl (b), C(CH 3 )=CH 2 (c)). Complexes 3 are also obtained from the reactions of 2 with CHCl 3 in the presence of OH - in H 2 O. The reaction of trans-[IrBr(CH3)(-CH= CHPPh 3 ) 2 (CO)(PPh 3 )] + (4) with Ag + and 4-ethynyltoluene in the presence of NEt 3 gives a mixture of geometric isomers, 3a (where the CH 3 group is cis to -C≡C-p-C 6 H 4 CH 3 ligand) and 3'a (where the CH 3 group is trans to -C≡C-p-C 6 H 4 CH 3 ligand). Addition of aqueous HCl to 2a or 3a causes a new carbon-carbon bond formation between the methyl and alkynyl groups to produce cis-CH3CH=CH-p-C6H4CH3 (5) exclusively and [IrCl 2 (-CH=CHPPh 3 ) 2 -(PPh 3 )(L)] + (L = PPh 3 , CO).

Polymer−metal complexes composed of Cu(1,3-butadiene)OTf and cellulose acetate (CA), Cu−CA, have been successfully applied to facilitated olefin transport membranes for the olefin/paraffin separati...

The synthesis of dimethyl carbonate (DMC) by oxidative carbonylation of MeOH has been studied in the presence of various catalyst systems. The effect of catalyst composition on the catalytic activity and product composition is investigated. A three-component catalyst system composed of PdCl 2 (PPh 3 ) 2 , Cu(OMe) 2 and Me 4 NCl shows synergy effects in terms of the MeOH conversion (26%) and DMC selectivity (95%). The reaction performed in the presence of a single-component catalyst PdCl 2 (PPh 3 ) 2 produces dimethoxy methane (DMM) as a major product with selectivity over 90%, while the addition of Me 4 NCl or Cu(OMe) 2 to PdCl 2 (PPh 3 ) 2 results in the increase of DMC selectivity from 2% to 60%.

Hydroxide ion and alcohols or amines are added regioselectively to the −C⋮N and −CHCH2 groups of CH2CHCN in [Cp*Ir(η3-CH2CHCHPh)(NCCHCH2)]+ (1a). The unsaturated amido complex Cp*Ir(η3-CH2CHCHPh)(NHCOCHCH2) (2a), alkoxo amido complexes Cp*Ir(η3-CH2CHCHPh)(NHCOCH2CH2OR) (4, R = Me (a), Et (b)), amino amido complexes Cp*Ir(η3-CH2CHCHPh)(NHCOCH2CH2NR2) (6, R2 = Me2 (a), (Me)(H) (b)), and an amino imino−ether complex [Cp*Ir(η3-CH2CHCHPh)(NHC(OMe)CH2CH2NMe2)]+ (8) have been prepared from the reactions of 1a with OH-, OH-/ROH (R = Me, Et), OH-/HNR2 (R2 = Me2, (Me)(H)), and MeOH/NHMe2, respectively. Reactions of 2, 4, 6, and 8 with aqueous HCl yield Cp*IrCl(η3-CH2CHCHPh) and quantitative amounts of H2NCOCHCH2, H2NCOCH2CH2OR, H2NCOCH2CH2NR2, and MeOCOCH2CH2NMe2, respectively. Crystal structures of 1a and 4a have been determined by X-ray diffraction data analysis.

cis-Bis(alkenyl)iridium complexes cis,trans-[IrR(−CHCH+PPh3)2(CO)(PPh3)2]2+ (2, R = H (a), CH3 (b), Cl (c)) have been prepared from the reactions of dihaloiridium(III) compounds with HC⋮CH and PPh3...

Reactions of [Cp*Ir(η3-CH2CHCHPh)(NCMe)]OTf (1) with protic amines, alcohols, and water produce amidine complexes [Cp*Ir(η3-CH2CHCHPh)(NHC(NR2)Me)]OTf (2) (R2 = (Me)2 (a), (Me)(H) (b), (i-Pr)(H) (c), (−CH2(CH2)3CH2−) (d)), imino−ether complexes [Cp*Ir(η3-CH2CHCHPh)(NHC(OR‘)Me)]OTf (4) (R‘ = Me (a), Et (b), i-Pr (c)), and amido complex Cp*Ir(η3-CH2CHCHPh)(NHC(O)Me) (5-K), respectively. The keto form amido complex 5-K undergoes tautomerization to give the enol form complex Cp*Ir(η3-CH2CHCHPh)(NC(OH)Me) (5-E) in polar solvents. Tertiary amines (NMe3, NEt3) react with 1 in chlorinated solvents (XCl) to give the chloro complex Cp*IrCl(η3-CH2CHCHPh) (3) and quaternary ammonium salts [R3NX]OTf (R = Me, Et and X = CH2Cl, CH3, CHCl2, CCl3, PhCH2). Crystal structures of 2a, 4a, 5-K, and [Cp*Ir(NHC(OH)Me)(OH2)(PPh3)]OTf2 (6) have been determined by single-crystal X-ray diffraction analysis, which lead us to suggest hybrid structures, Ir−-NH−C(N+Me2)Me (2a‘) for 2a and Ir−-NH−C(O+Me)Me (4a‘) for 4a to some extent. Co...

Various factors affecting the oxidative carbonylation of aromatic amines were investigated in the presence of a catalyst system comprising SeO2 and alkali metal carbonate. An active catalyst, K2SeO3 was obtained from the reaction of SeO2 and K2CO3 in methanol and the activity was tested. The effects of added alkali metal salts, solvents, aromatic amine substrates, molar ratio of aniline to catalyst, temperature, and pressure on the catalytic activity were studied. The activation energy of the carbonylation of aniline was evaluated as 17.0 kcal/mol. The highest turnover frequency was found to be 2082/h at aniline/catalyst=12,800. A plausible mechanism for the carbonylation of aniline to diphenyl urea and phenyl carbamate has also been proposed.

Oxidative addition of H–R (H--Ph and H 2 ) to trans -Ir(--Ph)(CO)(PPh 3 ) 2 ( 2 ) gives the initial products, cis , cis -Ir(H)(--Ph) 2 (CO)(PPh 3 ) 2 ( 3a ) and cis , cis -Ir(H) 2 (--Ph)(CO)(PPh 3 ) 2 ( 3b ), respectively. Both cis -bis(PPh 3 ) complexes, 3a and 3b undergo isomerization to give the trans -bis(PPh 3 ) complexes, trans , trans -Ir(H)(--Ph) 2 (CO)(PPh 3 ) 2 ( 4a ) and cis , trans -Ir(H) 2 (--Ph)(CO)(PPh 3 ) 2 ( 4b ). The isomerization, 3b → 4b is first order with respect to 3b with k 1 =6.37×10 −4 s −1 at 25°C under N 2 in CDCl 3 . The reaction rate ( k 1 ) seems independent of the concentration of H 2 . A large negative entropy of activation (Δ S ≠ =−24.9±5.7 cal deg −1 mol −1 ) and a relatively small enthalpy of activation (Δ H ≠ =14.5±3.3 kcal mol −1 ) were obtained in the temperature range 15∼35°C for the isomerization, 3b → 4b under 1 atm of H 2 .

The iridium(III) complexes, 1–3, which are the key intermediates for a variety of well established reaction pathways for the metal-catalyzed reactions of alkynes such as oligomerization or polymerization, have been characterized by X-ray absorption spectroscopic analysis. According to the Ir LIII-edge X-ray absorption spectra for those complexes, the white lines for all the complexes represent a single peak, which suggests that the iridium(III) ions in the complexes are in a low spin state. From the least square fittings to XANES (X-ray absorption near edge structure) spectra, it has been found that the white line position for complex 3 is shifted to a lower energy side, and its area is smaller compared to the others, indicating that the ligand to metal charge transfer for the former becomes more significant than the latter. According to EXAFS (extended X-ray absorption fine structure) analyses, the spectral shapes clearly show the structural difference in the complexes between 1 or 2 and 3, which is well consistent with XANES results. The bond distances, d(Ir–C) and d(Ir–N), determined from EXAFS analyses, are reciprocally proportional to the IR frequencies, ν(C≡O) and ν(N≡C), of the corresponding ligands, indicating that the bonds, Ir–C and Ir–N, are competing with the bonds, C≡O and N≡C.

It is shown that temperature-programmed desorption of adsorbed NO on Co-ZSM-5 zeolite used in selective catalytic reduction can accurately measure the amount of Co2+ cation for Co/Al ratios from 0 to 0.42 where the 0.42 limit corresponds to 84% maximum exchange. Evidence is also shown for the formation of cobalt oxide particles in Co-ZSM-5 for Co/Al ratios above 0.42.

A wetness method preparation of Co/ZSM-5 catalysts for selective catalytic reduction of NO by propane is shown to be comparable to ion-exchange preparation at the optimum catalytic conversion temperature of 450°C and superior to ion-exchange preparation at lower temperatures. Modification of Co/ZSM-5 catalysts with Ca2+ or Sr2+ significantly improves the catalytic activity.

A kinetic investigation of the replacement of ClO4− in the complex [Ir(ClO4) (CO)(PPh3)2] with nitriles has shown somewhat different results from those found for the rhodium analogue. The rates of substitution reactions of Rh1 complexes are 102–103 times faster than those of the corresponding IrI complexes. The entropies of activation are ca 60 J mol−1 K−1 more negative for IrI complexes than for corresponding RhI complexes, suggesting an associative mechanism through the formation of a five-coordinated intermediate [Ir(ClO4)(NCR)(CO)(PPh3)2] for the reaction.

Catalytic hydrogenation of fused heteroaromatic compounds, acridine, quinoline and quinaldine, selectively occurs at the nitrogen containing rings to give 9,10-dihydroacridine, 1,2,3,4-tetrahydroquinoline and 1,2,3,4-tetrahydroquinaldine in the homogeneous solution prepared from the reaction of [Ir(COD)(PPh3)(PhCN)]ClO4 (COD=1,5-cyclooctadiene) with H2 (5 atm) at 50°C, while isoquinoline and indole are not hydrogenated under the same experimental conditions. In the presence of the rhodium analog [Rh(COD)(PPh3)(PhCN)]ClO4 however, both isoquinoline and indole are also hydrogenated at the nitrogen containing rings, which is understood in terms of heterogeneous catalysis by metallic rhodium powders produced in the reduction of the rhodium compound under the same experimental conditions (50°C, 5 atm of H2).

The iridium(O) carbonyl cluster, Ir4(CO)12 (1), and rhodium(O) carbonyl cluster, Rh6(CO)16 (2), were prepared from the reactions of [Ir(COD)(PhCN)2]BF4 (3) and [Rh(COD)(PhCN)2]BF4 (4) (COD = 1,5-cyclooctadiene) with CO (2 atm) and H2 (7 atm) at 100 °C in high yield (>95 %).

Reactions of PhC≡CH (1a) and p-CH 3 C 6 H 4 C≡CH (1b) with [Ir(RCN)(CO)(PPh 3 ) 2 ] ClO 4 , 2 (R=Ph (a), CH 3 (b), CH=CHPh (c)), give [Ir(H)(-C≡R')(RCN)(CO)(PPh 3 ) 2 ] ClO 4 , 3 (R'=Ph, R=Ph (a), CH 3 (b), CH=HPh (c); R'=p-CH 3 C 6 H 4 , R=Ph (d)), where the hydride is cis both to two PPh 3 groups and trans to RCN. The oxidative addition of 1a to 2a,b is first order both in 1a and 2a,b and depressed by the presence of RCN added

The complexes [Rh(CO)(PPh3)3]ClO41 and [Ir(cod)(PhCN)(PPh3)]ClO42(cod = cycloocta-1,5-diene), rapidly catalyse the double-bond migration of 2-ethylprop-2-en-1-ol 3 and prop-2-en-1-ol 4, respectively to generate a significant amount of the enols 2-methylbut-1-en-1-ol 5 and prop-1-en-1-ol 6 in the absence of a solvent and in CD3COCD3. Both enols 5 and 6 are quite stable and slowly undergo ketonization to the corresponding carbonyl compounds at room temperature in the absence of a solvent and in aprotic solvents. Detailed 1H NMR spectral data at 300 MHz suggest that two isomers (Z and E) of compound 5 are simultaneously produced in the reaction of 3 and 1, the ratio of the isomers (major:minor) being ca. 6–9 : 1. Reaction of compound 4 with 2 also generates the Z(major) and E isomers (minor product) of 6. The Z isomer initially generated rapidly undergoes isomerization to give the E isomer in the presence of 2, while both the Z and E isomers relatively slowly undergo ketonization. Additional 1H and 13C NMR and infrared spectral data for Me2CCHOD and Me2CDCHO are reported with some experimental details.

New cationic iridium(I) complexes, [Ir(cod)(PPh3)L]ClO41[cod = cycloocta-1,5-diene; L = PhCN, PhCHCHCN, CH2CHCN, CH2C(Me)CN, MeCHCHCN or CH2CHCH2CN co-ordinated through the nitrogen atom], have been prepared by the reactions of [IrCl(cod)(PPh3)] with AgClO4 in the presence of L. Reaction of [Ir(cod)(PPh3)(PhCN)]ClO41a with H2 gives the cis-dihydridoiridium(III) complex [IrH2(cod)(PPh3)(PhCN)]ClO42a where the two hydrides are trans to PhCN and an olefinic group of cod, respectively. Complex 2a is stable both in solution and in the solid state at low temperature and decomposes at 15 °C to give cyclooctane and unidentified Ir–cod complex(es). The nitrile (L) in 1 is readily replaced by both PPh3 and CO, while cod is replaced only by CO. In the presence of complexes 1, unsaturated alcohols such as CH2CHCH2OH, CH2CHCH(Me)OH and CH2CHCH(Ph)OH rapidly undergo isomerization to the corresponding saturated carbonyl compounds at room temperature. Complex 1a catalyses the hydrogenation of unsaturated aldehydes, PhCHCRCHO (R = H, Me or Cl) to give PhCHCRCH2OH, PhCH2CHRCHO and PhCH2CHRCH2OH under H2(pH2= 6 atm) at 50 °C.

Oligomerization of phenylacetylene is catalyzed by (Rh-1), (Rh-2), , Rh-3; , Rh-4; , Rh-5), (Rh-6), , , , , , Ir-5; COD, Ir-6 and 2,2'-dipyridyl, Ir-7), , , Ir-9 to produce dimerization products, 1,3-diphenylbut-1-yn-3-ene, 1, (E)-1,4-diphenylbut-1-yn-3-ene, 2 and (Z)-1,4-diphenylbut-1-yn-3-ene, 3, and cyclotrimerization products, 1,3,5-triphenylbenzene, 4 and 1,2,4-triphenylbenzene, 5. Product distribution of the oligomers varies depending on various factors such as the nature of catalysts, reaction temperature, counter anions and excess ligand present in the reaction mixtures. Increasing reaction temperature in general increases the yield of the cyclotrimerization products. Exclusive production of dimer 1 and trimer 4 can be obtained with Ir-1 at 0 C and with Ir-2 in the presence of excess PhCN (or ) at 50 C, respectively. Dimer 2 (up to 81%) and trimer 5 (up to 98%) are selectively produced with Rh-1 at 50 and 100 C respectively. Production of 3 is selectively increased up to 85% by using - salt of + at 25 C. Addition of to Rh-1 produces and increases the rate of oligomerization(disappearance of phenylacetylene). Among the metal compounds investigated in this study, Ir-1 catalyzes most rapidly the oligomerization where the catalytically active species seems to contain lr(PPh3)2 moiety. The stoichiometric reaction of phenylacetylene wth Ir-9 at 25 C quantitatively produces hydridophenyl-ethynyl iridium(III) complex, (Ir-11), which seems to be an intermediate for the oligomerization.

Stable alkynyl complexes of iridium(III) (LnIr-⋮-R) that are prepared from the reactions of terminal alkynes readily undergo the intramolecular C−C bond-forming reactions between the alkynyl and adjacent hydrocarbyl ligands to yield conjugated olefins. These reactions are initiated by electrophiles (H+, Me+) that attack the β carbon of the alkynyl ligand to increase the electrophilicity of the α carbon of the alkynyl ligand. The C−C bond is then formed between the α carbons of the alkynyl and adjacent hydrocarbyl ligands.

Reaction of [RhCl(CO)(SbPh3)2]1 with CH2CHCH2Br 2a gives the σ-allylrhodium(III) complex [Rh(σ-CH2CHCH2)Cl(Br)(CO)(SbPh3)2]3, while reactions of 1 with allyl halides and AgClO4 give η3-allylrhodium(III) complexes [Rh(η3-allyl)X(CO)(SbPh3)2]ClO44[allyl = CH2CHCH2, CH2CHCHMe (X = Br or Cl), CH2CMeCH2, or CH2CHCHPh (X = Cl)]. The complex [Rh(η3-CH2CHCH2)Br(CO)(SbPh3)2]ClO4 can also be prepared by the reaction of 3 with AgClO4. The complex [Rh(η3-CH2CHCH2)Cl(CO)(SbPh3)2]ClO4 reacts with alcohols, amines and triphenylphosphine to give 1 and allyl ethers, diallylamines and allylphosphonium perchlorate, respectively. Reactions of allyl halides with alcohols and amines are catalysed by the η3-allyl complexes 4 in the presence of ClO4–.

Reactions of cationic iridium(I)-COD (COD = 1,5-cyclooctadiene) complexes, [Ir(COD)(PhCN)(PPh3)]ClO4 (1), [Ir(COD)(PPh3)2]ClO4 (2) and [Ir(COD)(PhCN)2]ClO4 (3) with nitriles under H2 catalytically produce primary, secondary and tertiary amines. Hydrogenation of nitriles (RCN) gives HCl salts of amines (RCH2NH2HCl, (RCH2)2NH HCl) in CH2Cl2. Secondary and tertiary amines seem to be produced by the reactions of RCN with primary and secondary amines, respectively under H2 in the presence of catalysts. The hydrogenation in the presence of1 and2 is homogeneously catalyzed by soluble iridium-PPh3 complexes formed in the reactions of1 and2 with H2 and RCN whereas the hydrogenation in the presence of3 is heterogeneous by metallic iridium powders produced in the reduction of3 by H2.

The structural and spectroscopic properties of new heteroleptic iridium complexes having a biphenyl and two bipyridyl based ligands are reported; DFT calculations reveal that the HOMO is composed of the biphenyl and iridium d orbitals while the LUMO is localized mainly on the two bipyridyl based ligands.

Newly prepared hydrido iridium(III) complexes [Ir(ppy)(PPh3)2(H)L](0,+) (ppy = bidentate 2-phenylpyridinato anionic ligand; L = MeCN (1b), CO (1c), CN(-) (1d); H being trans to the nitrogen of ppy ligand) emit blue light at the emission lambda(max) (452-457, 483-487 nm) significantly shorter than those (468, 495 nm) of the chloro complex Ir(ppy)(PPh3)2(H)(Cl) (1a). Replacing ppy of 1a-d with F2ppy (2,4-difluoro-2-phenylpyridinato anion) and F2Meppy (2,4-difluoro-2-phenyl-m-methylpyridinato anion) brings further blue-shifts down to the emission lambda(max) at 439-441 and 465-467 nm with CIE color coordinates being x = 0.16 and y = 0.18-0.20 to display a deep-blue photoemission. No significant blue shift is observed by replacing PPh3 of 1a with PPh2Me to produce Ir(ppy)(PPh2Me)2(H)(Cl) (1aPPh 2Me), which displays emission lambda max at 467 and 494 nm. The chloro complexes, [Ir(ppy)(PPh3)2(Cl)(L)](0,+) (L = MeCN (2b), CO (2c), CN(-) (2d)) having a chlorine ligand trans to the nitrogen of ppy also emit deep-blue light at emission lambda(max) 452-457 and 482-487 nm.

The hydrogenation of C 6 H 5 CHCHCHO ( 1 ), C 6 H 5 CHC(CH 3 )CHO ( 6 ) and C 6 H 5 CHC(Cl)CHO ( 7 ) by Ir(ClO 4 )(CO)(PPh 3 ) 2 ( 2 ), IrCl(PPh 3 ) 3 ( 8 ), IrCl(CO)(PPh 3 ) 2 ( 9 ) and [Ir(CO)(PPh 3 ) 3 ]ClO 4 ( 10 ) occurs primarily at the carbonyl group to give unsaturated alcohols, C 6 H 5 CHCHCH 2 OH ( 5 ), C 6 H 5 CHC(CH 3 ) CH 2 OH ( 11 ) and C 6 H 5 CH  C(Cl)CH 2 OH ( 12 ) at 50°C under 9 atm of hydrogen. Compound 5 is isomerized to C 6 H 5 CH 2 CH 2 CHO ( 3 ) by 2 , 8 and 9 but not by 10 . The carbonyl group of 3 is further hydrogenated to produce the saturated alcohol, C 6 H 5 CH 2 CH 2 CH 2 OH ( 4 ) in the presence of 2 , 8 and 9 . The isomerizations: 5 → 3 by 10 , and 11 → C 6 H 5 CH 2 CH(CH 3 )CHO and 12 → C 6 H 5 CH 2 CH(Cl)CHO by 8 and 9 probably do not occur for steric reasons; the interaction between the internal olefinic group and the iridium with bulky ligands is hindered.

Reactions of the iridium(III) compounds [Ir(H)(−C⋮CPh)(PhCN)L3]+ (1) and [IrCHCHCHCH)(PhCN)L3]+ (2) (L3 = (CO)(PPh3)2) with HC⋮CH in the presence of NEt3 produce the acetylene-inserted products [Ir(H)(−C⋮CPh)(−CHCH+NEt3)L3]+ (3) and [IrCHCHCHCH)(−CHCH+NEt3)L3]+ (4), while those with HC⋮CPh give the alkynyl complexes Ir(H)(−C⋮CPh)2L3 (5) and IrCHCHCHCH)(−C⋮CPh)L3 (6).

Iridabenzenes [Ir{=CHCH= CHCH=C(CH 2 R)}(CH 3 CN) 2 (PPh 3 ) 2 ] 2 + (R=Ph 4a, R = p-C 6 H 4 CH 3 4b) are obtained from the reactions of H + with iridacyclohexadienes [Ir{-CH=CHCH= CHC(=CH-p-C 6 H 4 R')}(CO)(PPh 3 ) 2 ] + (R'=H 3a, R'=CH 3 3b), which are prepared from [2+2+1] cyclotrimerization of alkynes in the reactions of [Ir(CH 3 CN)(CO)(PPh 3 ) 2 ] + with HC≡ CH and HC≡CR. Iridabenzenes 4 react with CO and CH 3 CN in the presence of NEt 3 to give iridacyclohexadienes [Ir{-CH=CHCH=CHC(=CHR)}(CO) 2 -(PPh 3 ) 2 ] + (6) and [Ir{-CH=CHCH= CHC(=CHR)}(CH 3 CN) 2 (PPh 3 ) 2 ] + (7), respectively. Iridacyclohexadienes 6 and 7 also convert to iridabenzenes 4 by the reactions with H + in the presence of CH 3 CN. Alkynyl iridacyclohexadienes [Ir(-CH=CHCH=CHC(=CH-p-C 6 H 4 R')}(-C≡CH)(PPh 3 ) 2 ] (8) undergo a cleavage of C≡C bond by H + /H 2 O to produce [Ir{-CH=CHCH=CHC(= CH-p-C 6 H 4 R')}(-CH 3 )(CO)(PPh 3 ) 2 ] (10) via facile inter-conversion between iridacyclohexadienes and iridabenzenes.

A new hexanuclear rhenium cluster encapsulated by six iridium complexes, [Re6Te8(CN)6][(Ir(CO)(PPh3)2)6](OTf)2 (3), which is effective in catalyzing the hydrogenation of p-CH3C6H4C[triple bond]CH to p-CH3C6H4CH=CH2 has been prepared.