Yuji Ohgomori

Formation of 1,6-hexanedial via hydroformylation of 1,3-butadiene

Abstract Rhodium catalyst promoted by bidentate phosphine with natural bite angle being 102–113°, particularly DIOP, is effective for 1,6-hexanedial formation in the hydroformylation of butadiene.

Electronic and steric effects of phosphine ligands in the formation of ethylene glycolfrom synthesis gas catalyzed by rhodium

Abstract The catalytic activity of the rhodium/phosphine system in the formation of ethylene glycol from synthesis gas is determined by the electronic and steric effects of the phosphine ligands, including alkyl-substituted phosphorinane and alkyl diisopropylphosphine. Tafts substitution constant of the alkyl substituent and the 31 P NMR chemical shifts for the coordinated phosphine are used as the electronic and steric parameters, respectively. For both types of phosphine, the rate of ethylene glycol formation increases with an increase in the electron-donating effect of the alkyl substituent. The steric hindrance of the substituents in alkyl diisopropylphosphine inhibits the electronic effect for glycol formation.

Hydroformylation of acrolein acetal

Abstract Acrolein acetals were hydroformylated by the rhodium-triarylphosphine system. Excellent rates and selectivity to succinaldehyde monoacetal were obtained by using 4,4,6-trimethyl-2-vinyl-1,3-dioxane and tris(3,5-dichlorophenyl) phosphine as the acrolein acetal and phosphine ligand, respectively. Key roles of substituents of the phosphine and the acrolein acetal to promote the reaction are also discussed.

Promoting effect of acids on the formation of ethylene glycol from synthesis gas catalyzed by the rhodium-tricyclohexylphosphine system

Abstract Carboxylic acids, pentafluorophenol and phosphoric acid (HX) facilitate the formation of ethylene glycol from synthesis gas catalyzed by the rhodium-tricyclohexylphosphine (TCP) system. Complexes recovered from the resultant solutions were identified as RhX(CO)(TCP) 2 , which are stable to repeated use. The catalytically active species or its immediate precursor is proposed to be HRh(CO) 2 (TCP) 2 from IR spectroscopic analysis under synthesis gas pressure of 280 bar.

Synthesis and chemistry of trans-[RhX(CO)L2](X = anionic ligand, L = tertiary phosphine)

The novel preparation of a wide variety of trans-[RhX(CO) L2] complexes (X = anionic ligand, L = tertiary phosphine) from [Rh4(CO)12], phosphine (L), and acid (HX) is described. A plausible formation pathway is proposed. The electron density on the phosphorus atom in trans-[RhX(CO)L2] decreases and the length of the Rh–P bond increases with an increase in the electronegativity of the anionic ligand, X, in a cis position to the phosphine ligand. The rhodium complexes (X = arylcarboxylate) are reduced to afford rhodate anions such as [Rh(CO)3L]– and [Rh (CO)4]– in hexamethylphosphoramide solution under CO–H2. The rate of reduction increases with a decrease in the electron-withdrawing effect of the arylcarboxylate ligand.

Rhodium complexes possessing the unidentate anion of 2,4-pentanedione as a ligand; X-ray crystal structure of carbonyl(2,4-pentanedionato-O)bis(tri-isopropylphosphine)rhodium(I)

Rhodium complexes having the unidentate anion of 2,4-pentanedione as a ligand have been synthesized by the reaction of [Rh(acac)(CO)2][Hacac = acetylacetone (2,4-pentanedione)] with highly basic tertiary phosphines. The X-ray crystallographic analysis revealed that the co-ordination chemistry about the Rh atom is square planar with two phosphine ligands in trans positions. The unidentate 2,4-pentanedionate ligand has a trans configuration with respect to the CC bond. Proton n.m.r. studies indicated a singlet resonance for the methine of the pentanedione anion, which is widely accepted as a proof of the cis configuration. In the i.r. spectra absorptions characteristic of the unidentate pentanedionate were observed in the 1 500–1 620 cm–1 region, but the ketonic absorptions were unusually low for αβ-unsaturated carbonyls.

The direct conversion of synthesis gas into ethylene glycol catalysed by RhX(CO)L2[X = anionic ligand, L = P(cyclo-C6H11)3 or PPri3]

Higher catalytic activities have been found for RhX(CO)L2 complexes compared to the Rh4(CO)12–L system (molar ratio L:Rh 2:1) for the formation of ethylene glycol from synthesis gas.