The effects of pH on the molecular distribution of water soluble ruthenium(II) hydrides and its consequences on the selectivity of the catalytic hydrogenation of unsaturated aldehydes

Ferenc Joó, József Kovács, A. Bényei, A. Kathó

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Abstract

The effect of pH on the formation and equilibrium distribution of the water soluble ruthenium hydrides [HRuCl(TPPMS)2]2, [HRuCl(TPPMS)3] and [H2Ru(TPPMS)4] (TPPMS=(3-sulfonatophenyl)diphenylphosphine sodium salt) was studied in aqueous solution by pH-potentiometric and 1H and 31P NMR methods. Depending on the pH, [RuCl2(TPPMS)2]2 and its hydrido-derivatives hydrolyse extensively, giving rise to formation of hydroxo-ruthenium complexes. It was established that at pH≤3.3 the dominant ruthenium(II) species was [HRuCl(TPPMS)3], while at pH≥7 it was [H2Ru(TPPMS)4]. While [HRuCl(TPPMS)3] catalyzed the slow, selective hydrogenation of the C=C bond in trans-cinnamaldehyde, [H2Ru(TPPMS)4] was found an active and selective catalyst for C=O reduction. Consequently, the selectivity of the hydrogenation of trans-cinnamaldehyde could be completely inverted by minor changes in the solution pH, shifting the equilibrium between [HRuCl(TPPMS)3] and [H2Ru(TPPMS)4].

Original languageEnglish
Pages (from-to)441-448
Number of pages8
JournalCatalysis Today
Volume42
Issue number4
Publication statusPublished - Jul 23 1998

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Ruthenium
Aldehydes
Hydrides
Hydrogenation
Water
Catalyst selectivity
Salts
Sodium
Nuclear magnetic resonance
Derivatives
Catalysts
cinnamic aldehyde

ASJC Scopus subject areas

  • Catalysis
  • Process Chemistry and Technology

Cite this

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title = "The effects of pH on the molecular distribution of water soluble ruthenium(II) hydrides and its consequences on the selectivity of the catalytic hydrogenation of unsaturated aldehydes",
abstract = "The effect of pH on the formation and equilibrium distribution of the water soluble ruthenium hydrides [HRuCl(TPPMS)2]2, [HRuCl(TPPMS)3] and [H2Ru(TPPMS)4] (TPPMS=(3-sulfonatophenyl)diphenylphosphine sodium salt) was studied in aqueous solution by pH-potentiometric and 1H and 31P NMR methods. Depending on the pH, [RuCl2(TPPMS)2]2 and its hydrido-derivatives hydrolyse extensively, giving rise to formation of hydroxo-ruthenium complexes. It was established that at pH≤3.3 the dominant ruthenium(II) species was [HRuCl(TPPMS)3], while at pH≥7 it was [H2Ru(TPPMS)4]. While [HRuCl(TPPMS)3] catalyzed the slow, selective hydrogenation of the C=C bond in trans-cinnamaldehyde, [H2Ru(TPPMS)4] was found an active and selective catalyst for C=O reduction. Consequently, the selectivity of the hydrogenation of trans-cinnamaldehyde could be completely inverted by minor changes in the solution pH, shifting the equilibrium between [HRuCl(TPPMS)3] and [H2Ru(TPPMS)4].",
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T1 - The effects of pH on the molecular distribution of water soluble ruthenium(II) hydrides and its consequences on the selectivity of the catalytic hydrogenation of unsaturated aldehydes

AU - Joó, Ferenc

AU - Kovács, József

AU - Bényei, A.

AU - Kathó, A.

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N2 - The effect of pH on the formation and equilibrium distribution of the water soluble ruthenium hydrides [HRuCl(TPPMS)2]2, [HRuCl(TPPMS)3] and [H2Ru(TPPMS)4] (TPPMS=(3-sulfonatophenyl)diphenylphosphine sodium salt) was studied in aqueous solution by pH-potentiometric and 1H and 31P NMR methods. Depending on the pH, [RuCl2(TPPMS)2]2 and its hydrido-derivatives hydrolyse extensively, giving rise to formation of hydroxo-ruthenium complexes. It was established that at pH≤3.3 the dominant ruthenium(II) species was [HRuCl(TPPMS)3], while at pH≥7 it was [H2Ru(TPPMS)4]. While [HRuCl(TPPMS)3] catalyzed the slow, selective hydrogenation of the C=C bond in trans-cinnamaldehyde, [H2Ru(TPPMS)4] was found an active and selective catalyst for C=O reduction. Consequently, the selectivity of the hydrogenation of trans-cinnamaldehyde could be completely inverted by minor changes in the solution pH, shifting the equilibrium between [HRuCl(TPPMS)3] and [H2Ru(TPPMS)4].

AB - The effect of pH on the formation and equilibrium distribution of the water soluble ruthenium hydrides [HRuCl(TPPMS)2]2, [HRuCl(TPPMS)3] and [H2Ru(TPPMS)4] (TPPMS=(3-sulfonatophenyl)diphenylphosphine sodium salt) was studied in aqueous solution by pH-potentiometric and 1H and 31P NMR methods. Depending on the pH, [RuCl2(TPPMS)2]2 and its hydrido-derivatives hydrolyse extensively, giving rise to formation of hydroxo-ruthenium complexes. It was established that at pH≤3.3 the dominant ruthenium(II) species was [HRuCl(TPPMS)3], while at pH≥7 it was [H2Ru(TPPMS)4]. While [HRuCl(TPPMS)3] catalyzed the slow, selective hydrogenation of the C=C bond in trans-cinnamaldehyde, [H2Ru(TPPMS)4] was found an active and selective catalyst for C=O reduction. Consequently, the selectivity of the hydrogenation of trans-cinnamaldehyde could be completely inverted by minor changes in the solution pH, shifting the equilibrium between [HRuCl(TPPMS)3] and [H2Ru(TPPMS)4].

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