The effect of pH on the reactions of catalytically important RhI complexes in aqueous solution: Reaction of [RhCl(tppms)3] and trans-[RhCl(CO)(tppms)2] with hydrogen (TPPMS = mono-sulfonated triphenylphosphine)

Ferenc Joó, József Kovács, A. Bényei, L. Nadasdi, Gábor Laurenczy

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Abstract

Hydrolysis and hydrogenation of [RhCl(tppms)3] (1) and trans-[RhCl(CO)(tppms)2] (2) was studied in aqueous solutions in a wide pH range (22-(tppms)3] (3a,b) while in strongly basic solutions [RhH(H2O)(tppms)3] (4) is obtained, the midpoint of the equilibrium between these hydride species being at pH 8.2. The paper gives the first successful 1H and 31P NMR spectroscopic characterization of a water soluble rhodium(I)-monohydride (4) bearing only monodentate phosphine ligands. Hydrolysis of 2 is negligible below pH 9 and its hydrogenation results in formation of [Rh(CO)H(tppms)3] (5), which is an analogue to the well known and industrially used hydroformylation catalyst [Rh(CO)H(tppts)3] (6) (TPPTS = 3,3′,3″-phosphinetriyltris(benzenesulfonic acid) trisodium salt). It was shown by pH-potentiometric measurements that formation of 5 is strongly pH dependent in the pH 5-9 range; this gives an explanation for the observed but previously unexplained pH dependence of several hydroformylation reactions. Conversely, the effect of pH on the rate of hydrogenation of maleic and fumaric acid catalyzed by 1 in the 2 <pH <7 range can be adequately described by considering solely the changes in the ionization state of these substrates. All these results warrant the use of buffered (pH-controlled) solutions for aqueous organometallic catalysis.

Original languageEnglish
Pages (from-to)193-199
Number of pages7
JournalChemistry - A European Journal
Volume7
Issue number1
Publication statusPublished - Jan 5 2001

Fingerprint

Carbon Monoxide
Hydrogenation
Hydroformylation
Hydrogen
phosphine
Hydrolysis
Bearings (structural)
Rhodium
Acids
Organometallics
Hydrides
Catalysis
Ionization
Salts
Ligands
Nuclear magnetic resonance
Catalysts
Water
Substrates
triphenylphosphine

Keywords

  • Biphasic catalysis
  • Hydrides
  • Hydroformylation
  • Hydrogenation
  • Rhodium

ASJC Scopus subject areas

  • Chemistry(all)

Cite this

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title = "The effect of pH on the reactions of catalytically important RhI complexes in aqueous solution: Reaction of [RhCl(tppms)3] and trans-[RhCl(CO)(tppms)2] with hydrogen (TPPMS = mono-sulfonated triphenylphosphine)",
abstract = "Hydrolysis and hydrogenation of [RhCl(tppms)3] (1) and trans-[RhCl(CO)(tppms)2] (2) was studied in aqueous solutions in a wide pH range (22-(tppms)3] (3a,b) while in strongly basic solutions [RhH(H2O)(tppms)3] (4) is obtained, the midpoint of the equilibrium between these hydride species being at pH 8.2. The paper gives the first successful 1H and 31P NMR spectroscopic characterization of a water soluble rhodium(I)-monohydride (4) bearing only monodentate phosphine ligands. Hydrolysis of 2 is negligible below pH 9 and its hydrogenation results in formation of [Rh(CO)H(tppms)3] (5), which is an analogue to the well known and industrially used hydroformylation catalyst [Rh(CO)H(tppts)3] (6) (TPPTS = 3,3′,3″-phosphinetriyltris(benzenesulfonic acid) trisodium salt). It was shown by pH-potentiometric measurements that formation of 5 is strongly pH dependent in the pH 5-9 range; this gives an explanation for the observed but previously unexplained pH dependence of several hydroformylation reactions. Conversely, the effect of pH on the rate of hydrogenation of maleic and fumaric acid catalyzed by 1 in the 2",
keywords = "Biphasic catalysis, Hydrides, Hydroformylation, Hydrogenation, Rhodium",
author = "Ferenc Jo{\'o} and J{\'o}zsef Kov{\'a}cs and A. B{\'e}nyei and L. Nadasdi and G{\'a}bor Laurenczy",
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T2 - Reaction of [RhCl(tppms)3] and trans-[RhCl(CO)(tppms)2] with hydrogen (TPPMS = mono-sulfonated triphenylphosphine)

AU - Joó, Ferenc

AU - Kovács, József

AU - Bényei, A.

AU - Nadasdi, L.

AU - Laurenczy, Gábor

PY - 2001/1/5

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