Chong Shik Chin

Hydrogenation of nitriles with iridium-triphenylphosphine complexes

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.

Ligand Effects on Luminescence of New Type Blue Light-Emitting Mono(2-phenylpyridinato)iridium(III) Complexes

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.

Regioselective catalytic hydrogenation of nitrogen rings of fused heteroaromatic compounds with an iridium-triphenylphosphine complex

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 effects of catalyst composition on the catalytic production of dimethyl carbonate

Abstract 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%.

Selective hydrogenation of the carbonyl group of α,β-unsaturated aldehydes to alcohols with iridium(I) complexes

Abstract 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.

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.

Spectra, formation constants, reactions and catalytic activities of nitrogen-bonded unsaturated nitrile complexes of rhodium(I)

Abstract Cationic rhodium(I) complexes, [RhL(CO)(PPh3)2]ClO4 (L = CH2 = C(CH3)CN, cis-CH3CHCHCN, trans-CH3CHCHCN, CH2CHCH2CN; PPh3 = P(C6H5)3) have been prepared by the reactions of Rh(ClO4)(CO)(PPh3)2 with L. Spectral data suggest that L is coordinated to rhodium through the nitrogen atom. Formation constants for the reaction: Rh(ClO4)(CO)(PPh3)2 + L α [RhL(CO)(PPh3)2]ClO4 have been measured to be 2.93 × 105 M−1 (L = cis-CH3CHCHCN), 2.12 × 105 M−1 (L = CH2CHCH2CN), 1.97 × 105 M−1 (L = trans-CH3CHCHCN), 5.61 × 104 M−1 (L = CH2CHCN) and 4.77 × 104 M−1 (L = CH2C(CH3)CN) at 25°C in monochlorobenzene. Both complexes with L = CH3CHCHCN (cis and trans) show catalytic activities for the hydrogenation of CH3CHCHCN to CH3CH2CH2CN at 30°C while complexes with L = CH2CHCH2CN and CH2C(CH3)CN do not catalyze the hydrogenation of L at 30°C. It was found that the hydrogenation of CH3CHCHCN with complexes (L= CH3CHCHCN) is faster than that of CH2CHCN with the complex (L = CH2CHCN) while the oligomerization of CH3CHCHCN is slower than that of CH2CHCN.

Diastereocontrolled synthesis of cis-olefins by selective C–C bond formation between alkyl and alkynyl groups coordinated to “Ir(CHCHPPh3)(CO)(PPh3)2”

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.

Wetness method preparation of catalysts for selective catalytic reduction of NO by propane

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.

Facile insertion of alkynes into Ir–P (phosphine) and Ir–as (arsine) bonds: second and third alkyne addition to mononuclear iridium complexes

Alkynes (HCCH, PhCCH) insert into Ir–P (phosphine) and Ir–As (arsine) bonds of [Ir(H)(CCPh)(L3)(MPh3)]+ and [[graphic omitted]H)(MeCN)(L3)]+ in the presence of MPh3, to produce [Ir(H)(CCPh)(L3)(CHCHR–M + Ph3)]+ and [[graphic omitted]H)(L3(CHCHR–M+Ph3)]+[R = H, Ph; L3=(CO)(PPh3)2; M = P, As].