Masaru Ishino

Selective reduction of aromatic nitro compounds affording aromatic amines under CO/H2O conditions catalyzed by phosphine-added rhodium and ruthenium carbonyl complexes

Abstract High catalytic activities for the selective reduction of aromatic nitro compounds to the corresponding amines under the mild reaction conditions of room temperature and 1 atm of CO were found to be exhibited by chelatephosphine (dppe, dppm, etc.; dppe: 1,2-bis(diphenylphosphino)ethane, dppm: bis(diphenylphosphino)methane)-added rhodium and ruthenium carbonyl complexes in a 5 N NAOH aqueous solution. The reduction proceeded not only with high catalytic activities, but also with remarkably high nitro group selectivities; for example, 1-nitroanthraquinone afforded 1-aminoanthraquinone without other unsaturated groups (such as CO) being reduced. PR 3 -added Rh(CO) 2 (acac) complexes (PR 3 : PEtPh 2 , PEt 2 Ph, PEt 3 , etc.; acac: acetylacetonato) in diglyme in a 5 N NaOH aqueous solution were also found to show significant catalytic activities for the reduction of aromatic nitro compounds under mild CO/H 2 O conditions. Both electronic and steric factors of phosphine ligands are important in making this reaction proceed at such remarkable rates.

A new catalyst for the direct synthesis of ethylene glycol from carbon monoxide and hydrogen

Abstract Bulky alkylphosphines (with large cone angles around the P atom), such as P-i-Pr 3 (L), prominently enhance the activity and the stability of the rhodium carbonyl catalyst in the direct synthesis of ethylene glycol from carbon monoxide and hydrogen. Arylphosphines, alkyl- and aryl-phosphites and also alkylphosphines with small cone angles, such as P-n-Bu 3 , all decompose to form the phosphidocarbonyl cluster anion, [Rh 9 P(CO) 21 ] 2− and hence inhibit the catalysis. High pressure IR analysis indicates that HRh(CO) 3 L, rather than anionic rhodium carbonyl clusters, plays an important role in the formation of ethylene glycol. Thus 0.3 mg-atom of Rh 4 (CO) 12 and 0.3 mmol of P-i-Pr 3 in 7.5 ml of 1-methyl-2-pyrrolidinone were allowed to react at 220°C in an autoclave and under 450 kg cm −2 H 2 /CO pressure for 3 h. Turn-over frequencies for ethylene glycol and methanol were 6.2 and 4.3, respectively, and selectivity was 58.8%.

1-Alkylbenzimidazoles as unique promoters for a homogeneous ruthenium catalyst for direct ethylene glycol formation from synthesis gas

Abstract 1-Alkylbenzimidazoles such as 1-methylbenzimidazole and 1,5,6-trimethylbenzimidazole have been found to be excellent promoters for direct ethylene glycol formation from hydrogen and carbon monoxide in the presence of a homogeneous ruthenium catalyst. High pressure IR analyses revealed that three Ru species, [HRu 3 (CO) 11 ] − (I), Ru(CO) 5 (II) and Ru(CO) 4 (1-alkylbenzimidazole) (III) had formed. An analysis of the relationship between activity and identity of Ru species showed that ruthenium species III plays an important role in ethylene glycol formation, and that the high coordination ability of benzimidazoles is essential to the promoting effect on ethylene glycol formation.

Effect of phosphine ligands on homogeneous hydrogenation of carbon monoxide by iridium catalysts

Abstract During the hydrogenation of carbon monoxide by carbonyl iridium catalyst under high pressure, triarylphosphines such as triphenylphosphine were found to enhance the activity and selectivity for ethylene glycol formation, whereas trialkylphosphines mostly promoted methanol formation. The moderate σ-donating ability of the ligand appears to be important for ethylene glycol formation. Crystalline Ir2(CO)6(PPh3)2 was isolated from the reaction mixture. This complex by itself showed a high catalytic activity for ethylene glycol.

Efficient synthesis of 2,3-dimethylbutenes by dimerization of propylene using nickel-phosphine catalyst in the presence of strong sulfonic acids and/or dialkyl sulfates. Remarkable effect of strong sulfonic acids and/or dialkyl sulfates

Abstract Remarkable catalytic activities as well as high selectivities have been found for dimerization of propylene catalyzed by the nickel-phosphine system composed of nickel naphthenate/P(cyclo-C 6 H 11 ) 3 /AlEt 3 /2,4,6-trichlorophenol (TCP) especially in the presence of strong sulfonic acids (CF 3 SO 3 H, MeSO 3 H) or dialkyl sulfates (Me 2 SO 4 and Et 2 SO 4 ). The catalytic activity was further increased upon the combination of these effective additives. The desired C 6 olefins such as 2,3-dimethylbut-1-ene (DMB-1), 2,3-dimethylbut-2-ene (DMB-2, TMEN) could be obtained in relatively high yields by using these catalysts (selectivity of dimers = 70–80%: selectivity of dimethylbutenes in C 6 olefins = ∼80%). The ratio of DMB-1/TMEN could be controlled without changing the catalytic activities by varying the molar ratios of catalyst precursors. CF 3 SO 3 H was found to be the most effective additive for increasing the reaction rate, although the selectivity of dimethylbutenes decreased significantly. Addition of a small amount of water enhanced the reaction rate significantly (turnover numbers for 2,3-dimethylbutenes: 7046 → 30358). The importance of these catalyst systems should be emphasized, because the amount of nickel species required can be minimized compared with that required for the conventional process.

Efficient dimerization of propylene affording 2,3-dimethylbutenes by fluorinated alcohol modified nickel-phosphine catalyst system containing strong sulfonic acid and/or dialkyl sulfates

A remarkable increase of both catalytic activity and the selectivity of dimers has been found for propylene dimerization affording 2,3-dimethylbutenes by a nickel-phosphine catalyst system composed of nickel naphthenate/P(cyclo-C6H11)3/A lEt3/ (CF3)2CHOH in the presence of CF3SO3H and/or Me2SO4: a combination of these effective additives also enhanced the reaction rates.

Ethylene glycol formation from carbon monoxide and hydrogen by homogeneous rhenium catalysts

Rhenium carbonyl, when combined with a halide or acetate salt, was found to exhibit catalytic activity for the direct formation of ethylene glycol from carbon monoxide and hydrogen in N-methylpyrrolidinone solvent under high pressure and temperature. LiCl was found to be the most effective salt. This is the first case in which a non-Group VIII element is reported to catalyze the reaction. IR spectroscopic studies revealed that the halides interact with rhenium in such a manner to increase the electron density of the central metal atom. Nickel was effective as a cocatalyst in promoting the ethylene glycol formation.