Cooperative catalysis of a trinuclear ruthenium(II) complex in transfer hydrogenation of ketones by formic acid

Yuichi Yano; Takahiko Kojima; Shunichi Fukuzumi

doi:10.1016/j.ica.2011.01.100

Cooperative catalysis of a trinuclear ruthenium(II) complex in transfer hydrogenation of ketones by formic acid

Yuichi Yano, Takahiko Kojima, Shunichi Fukuzumi

Department of Chemistry & Nanoscience

Research output: Contribution to journal › Article › peer-review

5 Scopus citations

Abstract

A novel TPA derivative (TPA = tris(2-pyridylmethyl)amine) having two 1,10-phenanthroline (phen) moieties via amide linkage was synthesized and this ligand reacted with [Ru(hmb)Cl₂]₂ (hmb: hexamethylbenzene) to give a trinuclear Ru(II) complex, [RuCl(TPA-{phenRuCl(hmb)} ₂-H⁺)](PF₆)₂ (1-Cl), in a moderate yield. The complex involves a deprotonated and oxygen-coordinated amide linkage, which exhibits reversible protonation-deprotonation equilibrium. The chlorido complex was converted to be an aqua complex, [Ru(H₂O)(TPA- {phenRu(H₂O)₂(hmb)}₂-H⁺)](SO ₄)_5/2 (1-H₂O), by the reaction of 1-Cl with Ag₂SO₄ in H₂O. Transfer hydrogenation of ketones was examined by using 1-Cl as a catalyst and HCOONa as a hydride source in H₂O/CH₃OH (1:1 v/v) at 50 °C under Ar. The time-course of the transfer hydrogenation of cyclohexanone to give cyclohexanol revealed that 1-Cl showed a cooperative effect on the catalytic reactivity as compared with that of mononuclear [RuCl(hmb)(phen)] (3-Cl) and [RuCl((1-Naph)₂-TPA)]PF₆ in H₂O/CH ₃OH (1:2 v/v) under the same conditions. The detailed kinetic study has revealed that the catalytic transfer hydrogenation proceeds via the formato complex, which interacts with a substrate rather than via the hydrido complex. The two Ru centers placed at close proximity in 1-H₂O enhanced the interaction of the formato complex with a substrate, resulting in an increase in the catalytic reactivity as compared with the mononuclear complex.

Original language	English
Pages (from-to)	104-111
Number of pages	8
Journal	Inorganica Chimica Acta
Volume	374
Issue number	1
DOIs	https://doi.org/10.1016/j.ica.2011.01.100
State	Published - 1 Aug 2011

Bibliographical note

Funding Information:
This work was supported by Grants-in-Aid (Nos. 21750146 , 21350035 and 20108010 ), a Global COE program, “the Global Education and Research Center for Bio-Environmental Chemistry” from the Japan Society of Promotion of Science (JSPS) , and by KOSEF/MEST through WCU project ( R31-2008-000-10010-0 ).

Keywords

Catalysis
Formic acid
Ketones
Ruthenium(II) complexes
Transfer hydrogenation

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title = "Cooperative catalysis of a trinuclear ruthenium(II) complex in transfer hydrogenation of ketones by formic acid",

abstract = "A novel TPA derivative (TPA = tris(2-pyridylmethyl)amine) having two 1,10-phenanthroline (phen) moieties via amide linkage was synthesized and this ligand reacted with [Ru(hmb)Cl2]2 (hmb: hexamethylbenzene) to give a trinuclear Ru(II) complex, [RuCl(TPA-{phenRuCl(hmb)} 2-H+)](PF6)2 (1-Cl), in a moderate yield. The complex involves a deprotonated and oxygen-coordinated amide linkage, which exhibits reversible protonation-deprotonation equilibrium. The chlorido complex was converted to be an aqua complex, [Ru(H2O)(TPA- {phenRu(H2O)2(hmb)}2-H+)](SO 4)5/2 (1-H2O), by the reaction of 1-Cl with Ag2SO4 in H2O. Transfer hydrogenation of ketones was examined by using 1-Cl as a catalyst and HCOONa as a hydride source in H2O/CH3OH (1:1 v/v) at 50 °C under Ar. The time-course of the transfer hydrogenation of cyclohexanone to give cyclohexanol revealed that 1-Cl showed a cooperative effect on the catalytic reactivity as compared with that of mononuclear [RuCl(hmb)(phen)] (3-Cl) and [RuCl((1-Naph)2-TPA)]PF6 in H2O/CH 3OH (1:2 v/v) under the same conditions. The detailed kinetic study has revealed that the catalytic transfer hydrogenation proceeds via the formato complex, which interacts with a substrate rather than via the hydrido complex. The two Ru centers placed at close proximity in 1-H2O enhanced the interaction of the formato complex with a substrate, resulting in an increase in the catalytic reactivity as compared with the mononuclear complex.",

keywords = "Catalysis, Formic acid, Ketones, Ruthenium(II) complexes, Transfer hydrogenation",

author = "Yuichi Yano and Takahiko Kojima and Shunichi Fukuzumi",

note = "Funding Information: This work was supported by Grants-in-Aid (Nos. 21750146 , 21350035 and 20108010 ), a Global COE program, “the Global Education and Research Center for Bio-Environmental Chemistry” from the Japan Society of Promotion of Science (JSPS) , and by KOSEF/MEST through WCU project ( R31-2008-000-10010-0 ). ",

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AU - Yano, Yuichi

AU - Kojima, Takahiko

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N1 - Funding Information: This work was supported by Grants-in-Aid (Nos. 21750146 , 21350035 and 20108010 ), a Global COE program, “the Global Education and Research Center for Bio-Environmental Chemistry” from the Japan Society of Promotion of Science (JSPS) , and by KOSEF/MEST through WCU project ( R31-2008-000-10010-0 ).

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N2 - A novel TPA derivative (TPA = tris(2-pyridylmethyl)amine) having two 1,10-phenanthroline (phen) moieties via amide linkage was synthesized and this ligand reacted with [Ru(hmb)Cl2]2 (hmb: hexamethylbenzene) to give a trinuclear Ru(II) complex, [RuCl(TPA-{phenRuCl(hmb)} 2-H+)](PF6)2 (1-Cl), in a moderate yield. The complex involves a deprotonated and oxygen-coordinated amide linkage, which exhibits reversible protonation-deprotonation equilibrium. The chlorido complex was converted to be an aqua complex, [Ru(H2O)(TPA- {phenRu(H2O)2(hmb)}2-H+)](SO 4)5/2 (1-H2O), by the reaction of 1-Cl with Ag2SO4 in H2O. Transfer hydrogenation of ketones was examined by using 1-Cl as a catalyst and HCOONa as a hydride source in H2O/CH3OH (1:1 v/v) at 50 °C under Ar. The time-course of the transfer hydrogenation of cyclohexanone to give cyclohexanol revealed that 1-Cl showed a cooperative effect on the catalytic reactivity as compared with that of mononuclear [RuCl(hmb)(phen)] (3-Cl) and [RuCl((1-Naph)2-TPA)]PF6 in H2O/CH 3OH (1:2 v/v) under the same conditions. The detailed kinetic study has revealed that the catalytic transfer hydrogenation proceeds via the formato complex, which interacts with a substrate rather than via the hydrido complex. The two Ru centers placed at close proximity in 1-H2O enhanced the interaction of the formato complex with a substrate, resulting in an increase in the catalytic reactivity as compared with the mononuclear complex.

AB - A novel TPA derivative (TPA = tris(2-pyridylmethyl)amine) having two 1,10-phenanthroline (phen) moieties via amide linkage was synthesized and this ligand reacted with [Ru(hmb)Cl2]2 (hmb: hexamethylbenzene) to give a trinuclear Ru(II) complex, [RuCl(TPA-{phenRuCl(hmb)} 2-H+)](PF6)2 (1-Cl), in a moderate yield. The complex involves a deprotonated and oxygen-coordinated amide linkage, which exhibits reversible protonation-deprotonation equilibrium. The chlorido complex was converted to be an aqua complex, [Ru(H2O)(TPA- {phenRu(H2O)2(hmb)}2-H+)](SO 4)5/2 (1-H2O), by the reaction of 1-Cl with Ag2SO4 in H2O. Transfer hydrogenation of ketones was examined by using 1-Cl as a catalyst and HCOONa as a hydride source in H2O/CH3OH (1:1 v/v) at 50 °C under Ar. The time-course of the transfer hydrogenation of cyclohexanone to give cyclohexanol revealed that 1-Cl showed a cooperative effect on the catalytic reactivity as compared with that of mononuclear [RuCl(hmb)(phen)] (3-Cl) and [RuCl((1-Naph)2-TPA)]PF6 in H2O/CH 3OH (1:2 v/v) under the same conditions. The detailed kinetic study has revealed that the catalytic transfer hydrogenation proceeds via the formato complex, which interacts with a substrate rather than via the hydrido complex. The two Ru centers placed at close proximity in 1-H2O enhanced the interaction of the formato complex with a substrate, resulting in an increase in the catalytic reactivity as compared with the mononuclear complex.

KW - Catalysis

KW - Formic acid

KW - Ketones

KW - Ruthenium(II) complexes

KW - Transfer hydrogenation

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Cooperative catalysis of a trinuclear ruthenium(II) complex in transfer hydrogenation of ketones by formic acid

Abstract

Bibliographical note

Keywords

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