Pyridine-2,6-bis(thioether) (SNS) Complexes of Ruthenium as Catalysts for Transfer Hydrogenation

Michael J. Page; Jörg Wagler; Barbara A. Messerle

doi:10.1021/om1005319

Pyridine-2,6-bis(thioether) (SNS) Complexes of Ruthenium as Catalysts for Transfer Hydrogenation

Michael J. Page, Jörg Wagler, Barbara A. Messerle

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

31 Citations (Scopus)

Abstract

Coordination of the pincer ligand 2,6-bis(tert-butylthiomethyl)pyridine (SNS ^tBu) to Ru(PPh ₃) ₃Cl ₂ and Ru(MeCN) ₄Cl ₂ led to the isolation of the complexes Ru(SNS ^tBu)Cl ₂(PPh ₃) (1) and Ru(SNS ^tBu)Cl ₂(MeCN) (4), respectively. Substitution of one chloride ligand from 1 and 4 with acetonitrile proved facile via salt metathesis with NaBPh ₄ to yield [Ru(SNS ^tBu)Cl(MeCN)(PPh ₃)]BPh ₄ (2) and [Ru(SNS ^tBu)Cl(MeCN) ₂]BPh ₄ (5). Reaction of 1 with an excess of AgBF ₄ in acetonitrile afforded the dicationic complex [Ru(SNS ^tBu)(MeCN) ₂(PPh ₃)](BF ₄) ₂ (3); however reaction of 4 under analogous conditions afforded the unusual silver-bridged dimer [Ru(SNS ^tBu)(MeCN) ₂Cl] ₂[μ-Ag(MeCN) ₂] ₂(BF ₄) ₄ (6), which retained the second chloride ligand on ruthenium. The less sterically encumbered compounds 5 and 6 were shown to have fluxional conformational arrangements associated with an inversion of the tetrahedrally hybridized thioether centers. Compounds 1-4 were also investigated as catalysts for the transfer hydrogenation of acetophenone. Steric congestion within these complexes was found to negatively impact on catalyst activity, with the less sterically encumbered complexes yielding the highest activity. In the case of 4 an extremely high turnover frequency of ca. 87?000 h ^-1 was achieved for this reaction.

Original language	English
Pages (from-to)	3790-3798
Number of pages	9
Journal	Organometallics
Volume	29
Issue number	17
DOIs	https://doi.org/10.1021/om1005319
Publication status	Published - 13 Sept 2010
Externally published	Yes

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title = "Pyridine-2,6-bis(thioether) (SNS) Complexes of Ruthenium as Catalysts for Transfer Hydrogenation",

abstract = "Coordination of the pincer ligand 2,6-bis(tert-butylthiomethyl)pyridine (SNS tBu) to Ru(PPh 3) 3Cl 2 and Ru(MeCN) 4Cl 2 led to the isolation of the complexes Ru(SNS tBu)Cl 2(PPh 3) (1) and Ru(SNS tBu)Cl 2(MeCN) (4), respectively. Substitution of one chloride ligand from 1 and 4 with acetonitrile proved facile via salt metathesis with NaBPh 4 to yield [Ru(SNS tBu)Cl(MeCN)(PPh 3)]BPh 4 (2) and [Ru(SNS tBu)Cl(MeCN) 2]BPh 4 (5). Reaction of 1 with an excess of AgBF 4 in acetonitrile afforded the dicationic complex [Ru(SNS tBu)(MeCN) 2(PPh 3)](BF 4) 2 (3); however reaction of 4 under analogous conditions afforded the unusual silver-bridged dimer [Ru(SNS tBu)(MeCN) 2Cl] 2[μ-Ag(MeCN) 2] 2(BF 4) 4 (6), which retained the second chloride ligand on ruthenium. The less sterically encumbered compounds 5 and 6 were shown to have fluxional conformational arrangements associated with an inversion of the tetrahedrally hybridized thioether centers. Compounds 1-4 were also investigated as catalysts for the transfer hydrogenation of acetophenone. Steric congestion within these complexes was found to negatively impact on catalyst activity, with the less sterically encumbered complexes yielding the highest activity. In the case of 4 an extremely high turnover frequency of ca. 87?000 h -1 was achieved for this reaction.",

author = "Page, {Michael J.} and J{\"o}rg Wagler and Messerle, {Barbara A.}",

year = "2010",

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T1 - Pyridine-2,6-bis(thioether) (SNS) Complexes of Ruthenium as Catalysts for Transfer Hydrogenation

AU - Page, Michael J.

AU - Wagler, Jörg

AU - Messerle, Barbara A.

PY - 2010/9/13

Y1 - 2010/9/13

N2 - Coordination of the pincer ligand 2,6-bis(tert-butylthiomethyl)pyridine (SNS tBu) to Ru(PPh 3) 3Cl 2 and Ru(MeCN) 4Cl 2 led to the isolation of the complexes Ru(SNS tBu)Cl 2(PPh 3) (1) and Ru(SNS tBu)Cl 2(MeCN) (4), respectively. Substitution of one chloride ligand from 1 and 4 with acetonitrile proved facile via salt metathesis with NaBPh 4 to yield [Ru(SNS tBu)Cl(MeCN)(PPh 3)]BPh 4 (2) and [Ru(SNS tBu)Cl(MeCN) 2]BPh 4 (5). Reaction of 1 with an excess of AgBF 4 in acetonitrile afforded the dicationic complex [Ru(SNS tBu)(MeCN) 2(PPh 3)](BF 4) 2 (3); however reaction of 4 under analogous conditions afforded the unusual silver-bridged dimer [Ru(SNS tBu)(MeCN) 2Cl] 2[μ-Ag(MeCN) 2] 2(BF 4) 4 (6), which retained the second chloride ligand on ruthenium. The less sterically encumbered compounds 5 and 6 were shown to have fluxional conformational arrangements associated with an inversion of the tetrahedrally hybridized thioether centers. Compounds 1-4 were also investigated as catalysts for the transfer hydrogenation of acetophenone. Steric congestion within these complexes was found to negatively impact on catalyst activity, with the less sterically encumbered complexes yielding the highest activity. In the case of 4 an extremely high turnover frequency of ca. 87?000 h -1 was achieved for this reaction.

AB - Coordination of the pincer ligand 2,6-bis(tert-butylthiomethyl)pyridine (SNS tBu) to Ru(PPh 3) 3Cl 2 and Ru(MeCN) 4Cl 2 led to the isolation of the complexes Ru(SNS tBu)Cl 2(PPh 3) (1) and Ru(SNS tBu)Cl 2(MeCN) (4), respectively. Substitution of one chloride ligand from 1 and 4 with acetonitrile proved facile via salt metathesis with NaBPh 4 to yield [Ru(SNS tBu)Cl(MeCN)(PPh 3)]BPh 4 (2) and [Ru(SNS tBu)Cl(MeCN) 2]BPh 4 (5). Reaction of 1 with an excess of AgBF 4 in acetonitrile afforded the dicationic complex [Ru(SNS tBu)(MeCN) 2(PPh 3)](BF 4) 2 (3); however reaction of 4 under analogous conditions afforded the unusual silver-bridged dimer [Ru(SNS tBu)(MeCN) 2Cl] 2[μ-Ag(MeCN) 2] 2(BF 4) 4 (6), which retained the second chloride ligand on ruthenium. The less sterically encumbered compounds 5 and 6 were shown to have fluxional conformational arrangements associated with an inversion of the tetrahedrally hybridized thioether centers. Compounds 1-4 were also investigated as catalysts for the transfer hydrogenation of acetophenone. Steric congestion within these complexes was found to negatively impact on catalyst activity, with the less sterically encumbered complexes yielding the highest activity. In the case of 4 an extremely high turnover frequency of ca. 87?000 h -1 was achieved for this reaction.

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U2 - 10.1021/om1005319

DO - 10.1021/om1005319

M3 - Article

AN - SCOPUS:77956406920

SN - 0276-7333

VL - 29

SP - 3790

EP - 3798

JO - Organometallics

JF - Organometallics

IS - 17

ER -

Pyridine-2,6-bis(thioether) (SNS) Complexes of Ruthenium as Catalysts for Transfer Hydrogenation

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