Synthesis and structural chemistry of arene-ruthenium half-sandwich complexes bearing an oxazolinyl–carbene ligand

Poyatos, Macarena; Maisse‐François, Aline; Bellemin‐Laponnaz, Stéphane; Peris, Eduardo; Gade, Lutz H.

doi:10.1016/j.jorganchem.2006.02.008

Cited by 58 publications

(33 citation statements)

References 47 publications

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“…6, 21 The average M1-Cl1 and M1-S1 distances are in agreement with other structurally characterised cationic  5 -Cp* rhodium or  6 -p-cymene ruthenium complexes reported in the Cambridge Structural Database. 22 Both ferrocene moieties have 45 eclipsed conformation and usual geometry.…”

supporting

confidence: 84%

“…The Rh1-C5 distance of 2.0550(17) Å compares well with related NHC-Cp* rhodium complexes. [20][21] The Ru1-C5 distance of 2.091(4) Å is slightly long but in the range of other NHC- 40 ruthenium complexes, which are found between 2.028(4) and 2.0828(14) Å.…”

mentioning

confidence: 89%

“…[20][21] The Ru1-C5 distance of 2.091(4) Å is slightly long but in the range of other NHC-40 ruthenium complexes, which are found between 2.028(4) and 2.0828(14) Å. 6,21 The average M1-Cl1 and M1-S1 distances are in agreement with other structurally characterised cationic  5 -Cp* rhodium or  6 -p-cymene ruthenium complexes reported in the Cambridge Structural Database.22 Both ferrocene moieties have 45 eclipsed conformation and usual geometry. …”

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confidence: 99%

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Rhodium(iii) and ruthenium(ii) complexes of redox-active, chelating N-heterocyclic carbene/thioether ligands

et al. 2011

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Dedicated to Professor Didier Astruc on the occasion of his 65th birthday.Half-sandwich rhodium(III) and ruthenium(II) complexes bearing a new redox-active ferrocenyl NHCthioether ligand have been prepared. The synthesis of ferrocenyl thioether-imidazolium salts 3a and 3b was carried out via intermediate 2 using an improved procedure. Rhodium(III) complex 4 and ruthenium(II) complex 5 were obtained in good yields and were fully characterised by NMR 10 spectroscopy, X-ray diffraction analysis and electrochemistry. Complex 4 shows a complex ABCD system by 1 H NMR, which denotes conformational rigidity due to the presence of several bulky groups.Electrochemical analysis by cyclic voltammetry reveals reversible redox behaviour about the iron centre in 4 and 5, and indicates electronic communication between iron and rhodium or ruthenium. Introduction 15N-Heterocyclic carbenes (NHCs) have become widely used ligands in many areas from transition metal catalysis, 1 organocatalysis, 2 to biochemistry and medicine. 3 They are generally described as organophosphine analogues, although their -donor character is more pronounced. Unlike phosphines, they 20 generally lead to air-stable, robust complexes which do not easily undergo ligand dissociation. However, the M-C bond stability could be detrimental to the catalytic activity. Functionalized Nheterocyclic carbene ligands combine the robust nature of the resulting metal-NHC bond with the flexibility of the secondary 25 donor function (hemilability, stereoelectronic control on the active site) and have been successfully used in many catalytic reactions. [4][5][6] However, any alteration of steric or electronic properties of a ligand implies structural modifications and thus more synthetic work. 30Fine tuning of the electronic properties can also be achieved by introduction of redox-active moieties in the ligands. 7 This has been demonstrated in the field of small molecule sensing 8,9 and in catalysis. 10 In the latter domain, transition metal complexes containing either substitutionally inert 11 or hemilabile 12 redox-35 active ligands have shown charge-dependent behaviour. Our group has a strong interest in the chemistry and catalytic activity of functionalised N-heterocyclic carbene complexes. We have shown that NHCs bearing thioether or phosphine donors give very efficient and robust catalysts. 13,14 The work reported 40 here describes the preparation of redox-active NHC-thioether ligands incorporating the ubiquitous ferrocene group and the study of their coordination chemistry and electrochemical behaviour. Results and discussion 45 SynthesisScheme 1 Synthesis of imidazolium salts 3a and 3b.The synthesis of the imidazolium salt 3b, i.e. the NHC-thioether precursor, was achieved in three steps from bromoferrocene 1. 50Although the preparation of intermediate 2 and its 1,1'-disubstituted analogue have been described by Mirkin et al., 15,16 we decided to follow a different synthetic route. Mirkin's reported procedures involved the monolithiation of ferrocene and afforded th...

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confidence: 89%

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confidence: 99%

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Rhodium(iii) and ruthenium(ii) complexes of redox-active, chelating N-heterocyclic carbene/thioether ligands

et al. 2011

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“…360 h -1 . This rate is competitive with other recently reported ruthenium-carbene complexes, [7,9] though considerably lower than the most active transfer hydrogenation catalysts, which have TOF 50 Ͼ 10,000 h -1 . [10] Since hydrogenation of the olefinic tether may constitute a potential catalyst (de)activation, [11] complex 5, comprised of an n-propyl wingtip group, was investigated as the saturated version of 1 (cf.…”

Section: Transfer Hydrogenation Of Ketonesmentioning

confidence: 46%

“…For example in iPrOH, hydrogen is formally provided through a proton, bound to oxygen, and a hydride-like carbinol hydrogen. [4] Based on this hypothesis and considering the privileged role of Ru(arene) scaffolds in (transfer) hydrogenation, [3b,3c,6] and specifically the success of the corresponding NHC-containing complexes in hydrogen transfer reactions, [7] we became interested in probing the activity of complexes 1-4 in transfer hydrogenation. A particularly intriguing aspect was the possibility of using a single complex for either direct or transfer hydrogenation of substrates.…”

Section: Introductionmentioning

confidence: 99%

Transfer Hydrogenation of Ketones and Activated Olefins Using Chelating NHC Ruthenium Complexes

2011

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N‐Heterocyclic carbene (NHC) ruthenium complexes consisting of different donor substituents attached to the NHC ligand efficiently catalyse the transfer hydrogenation of ketones and of activated olefins in α,β‐unsaturated ketones to give saturated alcohols. The most active catalyst precursor contains a tethered olefin as a hemilabile donor site. This complex also converts nitriles and, depending on the reaction conditions, either benzylamines are produced by means of transfer hydrogenation, or amides from formal addition of H2O. Kinetic analysis of the double hydrogenation of α,β‐unsaturated ketones indicates fast isomerisation of the enol intermediate to its saturated ketone tautomer prior to the second hydrogenation.

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N‐Heterocyclic Carbenes with Neutral Tethers

Kühl

2010

Functionalised N‐Heterocyclic Carbene Complexes

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Synthesis and structural chemistry of arene-ruthenium half-sandwich complexes bearing an oxazolinyl–carbene ligand

Cited by 58 publications

References 47 publications

Rhodium(iii) and ruthenium(ii) complexes of redox-active, chelating N-heterocyclic carbene/thioether ligands

Rhodium(iii) and ruthenium(ii) complexes of redox-active, chelating N-heterocyclic carbene/thioether ligands

Transfer Hydrogenation of Ketones and Activated Olefins Using Chelating NHC Ruthenium Complexes

N‐Heterocyclic Carbenes with Neutral Tethers

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