6-Halogenopyridin-2-olato complexes with the diruthenium(2+) core: Equilibria between head-to-head and head-to-tail structures

Schäffler, Lutz; Buck, Stefan De; Maas, Gerhard

doi:10.1016/j.ica.2007.06.016

Cited by 7 publications

(4 citation statements)

References 49 publications

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“…With the unsymmetrical amidate ligands, which coordinate by an N−C=O moiety, head-to-tail (or 1,1, e. g. 1 and 3) and head-tohead (or 0,2, e. g. 2 and 4) complexation is possible. Our investigations on saccharinato-(1 and 2 [12]) and 2-pyridinolato-(3 and 4 [3,10]) tetracarbonyldiruthenium(I,I) complexes have shown that the mutual conversion of the (1,1) and (0,2) arrangements of the equatorial bidentate ligands can occur smoothly at room c 2012 Verlag der Zeitschrift für Naturforschung, Tübingen · http://znaturforsch.com temperature during exchange of the axial ligands. For 6-halogenopyridin-2-olato complexes [Ru 2 (CO) 4 (µ-HalpyO) 2 (L 1/2 )], solvent-and temperature-dependent equilibria between (1,1) and (0,2) species could be observed in solution by NMR spectroscopy [3] in the temperature range where carbenoid reactions with these complexes as catalysts are usually performed.…”

Section: Introductionmentioning

confidence: 84%

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3,3’’-Bis(saccharin-6-ylmethyl)-1,1’:3’,1’’-terphenyl – Precursor of A New Tetradendate Bis-bridging Ligand

Buck¹,

Maas

2012

Zeitschrift Für Naturforschung B

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The title compound (H 2 tpsac) was synthesized from 6-bromosaccharin and 3,3 -bis(bromomethyl)-m-terphenyl. The ability of tpsac to serve as a tetradentate bis-bridging ligand was demonstrated by the formation of the dinuclear ruthenium(I,I) complexes [Ru 2 (CO) 5 (µ,µ-tpsac)] 2 , [Ru 2 (CO) 4 (µ,µ-tpsac)] n , [Ru 2 (CO) 4 (PPh 3 ) 2 (µ,µ-tpsac)], and [Ru 2 (CO) 5 (PPh 3 )(µ,µ-tpsac)]. An X-ray crystal structure analysis of [Ru 2 (CO) 4 (PPh 3 ) 2 (µ,µ-tpsac)] showed the head-to-tail (or 1,1) arrangement of the two saccharinate coordination sites.

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Section: Introductionmentioning

confidence: 84%

“…[2]; for a related Ru(I,I)-NHC complex, see ref. [3]). It has generally been assumed that the tetrabridged dinuclear framework of a rhodium-carbene remains intact during carbenoid reactions, and recent computational work seems to support this assumption (see, for example, refs.…”

Section: Introductionmentioning

confidence: 99%

3,3’’-Bis(saccharin-6-ylmethyl)-1,1’:3’,1’’-terphenyl – Precursor of A New Tetradendate Bis-bridging Ligand

Buck¹,

Maas

2012

Zeitschrift Für Naturforschung B

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“…To follow up on initial discovery of the catalyst 1NH 3 , supported by the 2-chloro-6-hydroxypyridinate (chp) equatorial ligand, we set out a broad experimental and computational research plan to examine the reactivity of Ru 2 and Os 2 complexes supported by related ligands 2-fluoro-6-hydroxypyridinate (fhp) and 2-hydroxy-6-methylpyridinate (hmp). The ligands chp − and fhp ,− have been previously used to support metal–metal bonded Ru 2 and Os 2 complexes; the hmp ligand has been used to support metal–metal bonded compounds of earlier transition metals having a similar paddlewheel-type structure. ,− A few Ru 2 complexes of hmp with related structures are known. ,, Computational results are reported here, while the experimental work will be reported elsewhere. We report computations on the parent [M 2 (ligand) 4 (NH 3 )] 0/+ compounds, including their predicted [M 2 ] 4+/5+ redox potentials, as well as mechanistic analyses of proposed intermediates having amido (NH 2 ), imido (NH), and nitrido (N) axial ligands (Table ).…”

Section: Introductionmentioning

confidence: 99%

Computational Analysis of Low Overpotential Ammonia Oxidation by Metal–Metal Bonded Ruthenium Catalysts, and Predictions for Related Osmium Catalysts

Trenerry,

Acosta,

Berry

2024

J. Phys. Chem. A

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The catalyzed electrochemical oxidation of ammonia to nitrogen (AOR) is an important fuel-cell half-reaction that underpins a future nitrogen-based energy economy. Our laboratory has reported spontaneous chemical and electrochemical oxidation of ammonia to dinitrogen via reaction of ammonia with the metal–metal bonded diruthenium complex Ru2(chp)4OTf (chp– = 2-chloro-6-hydroxypyridinate, TfO– = trifluoromethanesulfonate). This complex facilitates electrocatalytic ammonia oxidation at mild applied potentials of −255 mV vs ferrocene, which is the [Ru2(chp)4(NH3)]0/+ redox potential. We now report a comprehensive computational investigation of possible mechanisms for this reaction and electronic structure analysis of key intermediates therein. We extend this analysis to proposed second-generation electrocatalysts bearing structurally similar fhp and hmp (2-fluoro-6-hydroxypyridinate and 2-hydroxy-6-methylpyridinate, respectively) equatorial ligands, and we further expand this study from Ru2 to analogous Os2 cores. Predicted M2 4+/5+ redox potentials, which we expect to correlate with experimental AOR overpotential, depend strongly on the identity of the metal center, and to a lesser degree on the nature of the equatorial supporting ligand. Os2 complexes are easier to oxidize than analogous Ru2 complexes by ∼640 mV, on average. In contrast to mono-Ru catalysts, which oxidize ammonia via a rate-limiting activation of the strong N–H bond, we find lowest-energy reaction pathways for Ru2 and Os2 complexes that involve direct N–N bond formation onto electrophilic intermediates having terminal amido, imido, or nitrido groups. While transition state energies for Os2 complexes are high, those for Ru2 complexes are moderate and notably lower than those for mono-Ru complexes. We attribute these lower barriers to enhanced electrophilicity of the Ru2 intermediates, which is a consequence of their metal–metal bonded structure. Os2 intermediates are found to be, surprisingly, less electrophilic, and we suggest that Os2 complexes may require access to oxidation states higher than Os2 5+ in order to perform AOR at reasonable reaction rates.

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“…Deprotonated 2-pyridones have been used as ligands in transition metal complexes, particularly in the study of metalmetal bonded systems [an extensive review is provided by Cotton & Walton (1993); more recent examples include those reported by Villarroya et al (2005), Schä ffler et al (2006), Brown et al (2007), Schä ffler et al (2008, Harvey et al (2011)], in mixed complexes of transition metals and lanthanides (Winpenny, 1998;Huang et al, 2009), and in polynuclear clusters that behave as molecular magnets (Winpenny, 2001(Winpenny, , 2002Cadiou et al, 2003;Langley et al, 2012). Further interest has been fuelled by the recognition that mononuclear iron hydrogenase contains a 2-pyridone derivative in its active site (Shima et al, 2008;Tard & Pickett, 2009;Dey et al, 2013), leading, for example, to the development of other pyridone derivatives in bio-inspired catalysis (Wang et al, 2013).…”

Section: Introductionmentioning

confidence: 99%

Alkali metal complexes of 6-methyl-2-pyridone: simple formulae, but not so simple structures

Clegg

Tooke

2013

Acta Crystallogr Sect B

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Reaction of 6-methyl-2-pyridone (Hmhp) with Na or K metal, or with Rb or Cs 2-ethylhexoxide, in an appropriate single or mixed solvent, yields a series of solvated polymeric complexes with the empirical formulae M(mhp)(H2O)2 [(1), M = Na; (2), M = K], M(mhp)(H2O) [(3), M = Rb; (4), M = Cs] and Cs(mhp)(ROH) [(5), R = Me; (6), R = Et]. All of the products have been crystallographically characterized and show sheet polymeric structures, except for a double-chain structure for (2). In all of the structures, mhp(-) and solvent molecules function as bridging ligands; two metal ions are bridged (μ2) by each solvent molecule in (1), (5) and (6), while (2) contains both μ2 and μ3 triple bridges, and (3) and (4) display highly unusual μ4 quadruple bridging of metal ions by water molecules. The pyridonate O atom bridges two or three metal ions in each case. Nitrogen is also involved in coordination to the heavier metals; it bonds to a single ion in (3) and (4), but has an almost unprecedented bridging role in (5) and (6). As a result of the extensive bridging by ligands, coordination numbers between 6 and 8 are achieved for the metal ions. In each structure, all solvent OH groups form hydrogen bonds to pyridonate O and, in some cases, N atoms. With one exception, these are the first reported pyridonate complexes of the alkali metals Na-Cs that do not also include transition metals.

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6-Halogenopyridin-2-olato complexes with the diruthenium(2+) core: Equilibria between head-to-head and head-to-tail structures

Cited by 7 publications

References 49 publications

3,3’’-Bis(saccharin-6-ylmethyl)-1,1’:3’,1’’-terphenyl – Precursor of A New Tetradendate Bis-bridging Ligand

3,3’’-Bis(saccharin-6-ylmethyl)-1,1’:3’,1’’-terphenyl – Precursor of A New Tetradendate Bis-bridging Ligand

Computational Analysis of Low Overpotential Ammonia Oxidation by Metal–Metal Bonded Ruthenium Catalysts, and Predictions for Related Osmium Catalysts

Alkali metal complexes of 6-methyl-2-pyridone: simple formulae, but not so simple structures

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