Reactivity patterns and catalytic chemistry of iridium polyhydride complexes

Alan S Goldman, Jack Halpern

Research output: Contribution to journalArticle

37 Citations (Scopus)

Abstract

[IrH5P2] (1, P PPri 3) reacts autocatalytically with CF3COOR (R CH2CF3) in cyclo-C6D12 at 60°C according to: 1 + CF3COOR → [IrH2P2(OR)] (2) + ROH (4) (eq. 1). The rate-law, - d[1] dt = k[1] 1 2[CF3COOR][2] 1 2[4]- 1 2 (k = 1.25 × 10-4 M- 1 2 sec-1), is consistent with the mechanism, 1 + 2 ⇌ 2 [IrH3P2] (5) + 4 (rapid equilibrium); 5 + CF3COOR → [IrH2P2{OCH(OR)CF3}] (6) (rate determining); 6 → 2 + CF3CHO; 5 + CF3CHO → 2. 2 reacts rapidly with H2 (25° C, 1 atm) according to: 2 + 2 H2 → 1 + 4 (eq. 2). Although the combination of reactions 1 and 2 constitute a catalytic cycle for the hydrogenation of CF3COOR (CF3COOR + 2 H2 → 2 (4), catalyzed by 1), such catalytic hydrogenation does not occur, presumably because H2 suppresses reaction by rapidly converting the catalytic intermediates, 2 and 5, to 1. However, 1 was found to be effective as a catalyst or catalyst precursor for transfer hydrogenation, e.g. CH2CHC(CH3)3 + (CH3)2CHOH → CH3CH2C(CH3)3 + (CH3)2CO. While not directly detected, IrH3P2 could be trapped at low temperatures by N2 to yield the complexes [IrH3P2(N2)] and [(IrH3P2)2N2] which are related through the labile equilibrium, [(IrH3P2)2N2] + N2 ⇌ 2 [IrH3P2(N2)] (Keq ∼ 1.5 at 35° C).

Original languageEnglish
Pages (from-to)237-253
Number of pages17
JournalJournal of Organometallic Chemistry
Volume382
Issue number1-2
DOIs
Publication statusPublished - Feb 6 1990

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Iridium
Hydrogenation
iridium
hydrogenation
reactivity
chemistry
catalysts
Catalysts
cycles
Temperature

ASJC Scopus subject areas

  • Biochemistry
  • Chemical Engineering (miscellaneous)
  • Inorganic Chemistry
  • Organic Chemistry
  • Physical and Theoretical Chemistry
  • Materials Science (miscellaneous)
  • Materials Chemistry

Cite this

Reactivity patterns and catalytic chemistry of iridium polyhydride complexes. / Goldman, Alan S; Halpern, Jack.

In: Journal of Organometallic Chemistry, Vol. 382, No. 1-2, 06.02.1990, p. 237-253.

Research output: Contribution to journalArticle

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abstract = "[IrH5P2] (1, P PPri 3) reacts autocatalytically with CF3COOR (R CH2CF3) in cyclo-C6D12 at 60°C according to: 1 + CF3COOR → [IrH2P2(OR)] (2) + ROH (4) (eq. 1). The rate-law, - d[1] dt = k[1] 1 2[CF3COOR][2] 1 2[4]- 1 2 (k = 1.25 × 10-4 M- 1 2 sec-1), is consistent with the mechanism, 1 + 2 ⇌ 2 [IrH3P2] (5) + 4 (rapid equilibrium); 5 + CF3COOR → [IrH2P2{OCH(OR)CF3}] (6) (rate determining); 6 → 2 + CF3CHO; 5 + CF3CHO → 2. 2 reacts rapidly with H2 (25° C, 1 atm) according to: 2 + 2 H2 → 1 + 4 (eq. 2). Although the combination of reactions 1 and 2 constitute a catalytic cycle for the hydrogenation of CF3COOR (CF3COOR + 2 H2 → 2 (4), catalyzed by 1), such catalytic hydrogenation does not occur, presumably because H2 suppresses reaction by rapidly converting the catalytic intermediates, 2 and 5, to 1. However, 1 was found to be effective as a catalyst or catalyst precursor for transfer hydrogenation, e.g. CH2CHC(CH3)3 + (CH3)2CHOH → CH3CH2C(CH3)3 + (CH3)2CO. While not directly detected, IrH3P2 could be trapped at low temperatures by N2 to yield the complexes [IrH3P2(N2)] and [(IrH3P2)2N2] which are related through the labile equilibrium, [(IrH3P2)2N2] + N2 ⇌ 2 [IrH3P2(N2)] (Keq ∼ 1.5 at 35° C).",
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N2 - [IrH5P2] (1, P PPri 3) reacts autocatalytically with CF3COOR (R CH2CF3) in cyclo-C6D12 at 60°C according to: 1 + CF3COOR → [IrH2P2(OR)] (2) + ROH (4) (eq. 1). The rate-law, - d[1] dt = k[1] 1 2[CF3COOR][2] 1 2[4]- 1 2 (k = 1.25 × 10-4 M- 1 2 sec-1), is consistent with the mechanism, 1 + 2 ⇌ 2 [IrH3P2] (5) + 4 (rapid equilibrium); 5 + CF3COOR → [IrH2P2{OCH(OR)CF3}] (6) (rate determining); 6 → 2 + CF3CHO; 5 + CF3CHO → 2. 2 reacts rapidly with H2 (25° C, 1 atm) according to: 2 + 2 H2 → 1 + 4 (eq. 2). Although the combination of reactions 1 and 2 constitute a catalytic cycle for the hydrogenation of CF3COOR (CF3COOR + 2 H2 → 2 (4), catalyzed by 1), such catalytic hydrogenation does not occur, presumably because H2 suppresses reaction by rapidly converting the catalytic intermediates, 2 and 5, to 1. However, 1 was found to be effective as a catalyst or catalyst precursor for transfer hydrogenation, e.g. CH2CHC(CH3)3 + (CH3)2CHOH → CH3CH2C(CH3)3 + (CH3)2CO. While not directly detected, IrH3P2 could be trapped at low temperatures by N2 to yield the complexes [IrH3P2(N2)] and [(IrH3P2)2N2] which are related through the labile equilibrium, [(IrH3P2)2N2] + N2 ⇌ 2 [IrH3P2(N2)] (Keq ∼ 1.5 at 35° C).

AB - [IrH5P2] (1, P PPri 3) reacts autocatalytically with CF3COOR (R CH2CF3) in cyclo-C6D12 at 60°C according to: 1 + CF3COOR → [IrH2P2(OR)] (2) + ROH (4) (eq. 1). The rate-law, - d[1] dt = k[1] 1 2[CF3COOR][2] 1 2[4]- 1 2 (k = 1.25 × 10-4 M- 1 2 sec-1), is consistent with the mechanism, 1 + 2 ⇌ 2 [IrH3P2] (5) + 4 (rapid equilibrium); 5 + CF3COOR → [IrH2P2{OCH(OR)CF3}] (6) (rate determining); 6 → 2 + CF3CHO; 5 + CF3CHO → 2. 2 reacts rapidly with H2 (25° C, 1 atm) according to: 2 + 2 H2 → 1 + 4 (eq. 2). Although the combination of reactions 1 and 2 constitute a catalytic cycle for the hydrogenation of CF3COOR (CF3COOR + 2 H2 → 2 (4), catalyzed by 1), such catalytic hydrogenation does not occur, presumably because H2 suppresses reaction by rapidly converting the catalytic intermediates, 2 and 5, to 1. However, 1 was found to be effective as a catalyst or catalyst precursor for transfer hydrogenation, e.g. CH2CHC(CH3)3 + (CH3)2CHOH → CH3CH2C(CH3)3 + (CH3)2CO. While not directly detected, IrH3P2 could be trapped at low temperatures by N2 to yield the complexes [IrH3P2(N2)] and [(IrH3P2)2N2] which are related through the labile equilibrium, [(IrH3P2)2N2] + N2 ⇌ 2 [IrH3P2(N2)] (Keq ∼ 1.5 at 35° C).

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