Diastereoselective Protonation, Substitution and Addition Reactions at Pseudotetrahedral Rhenium Complexes

Bock, Frank; Fischer, Franz; Radacki, Krzysztof; Schenk, Wolfdieter A.

doi:10.1002/ejic.200901011

Cited by 10 publications

(2 citation statements)

References 43 publications

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“…41 Schenk has also noted in a study of rhenium complexes that the relative kinetics for protonation of a metal and amine-based ligand dominate over their relative basicities. 42 As such, availability of the pendant amines on the ligands of [Ni II (P 2 Ph N 2 Bn ) 2 ] 2+ , the relative basicity of these amines vs the metal center, and the rapid kinetics of ligand protonation enable the ligand-based PCET reaction to access equilibrium on the electrochemical time scale, giving rise to the potential−pK a relationships observed.…”

Section: Bnmentioning

confidence: 99%

Decoding Proton-Coupled Electron Transfer with Potential–pK_a Diagrams: Applications to Catalysis

2019

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The applied potential at which [NiII(P2 PhN2 Bn)2]2+ (P2 PhN2 Bn = 1,5-dibenzyl-3,7-diphenyl-1,5-diaza-3,7-diphosphacyclooctane) catalyzes hydrogen production is reported to vary as a function of proton source pK a in acetonitrile. By contrast, most molecular catalysts exhibit catalytic onsets at pK a-independent potentials. Using experimentally determined thermochemical parameters associated with reduction and protonation, a coupled Pourbaix diagram is constructed for [NiII(P2 PhN2 Bn)2]2+. One layer describes proton-coupled electron transfer reactivity involving ligand-based protonation, and the second describes metal-based protonation. An overlay of this diagram with experimentally determined E cat/2 values spanning 15 pK a units, along with complementary stopped-flow rapid mixing experiments to detect reaction intermediates, supports a mechanism in which the proton-coupled electron transfer processes underpinning the pK a-dependent catalytic processes involve protonation of the ligand, not the metal center. For proton sources with pK a values in the range 6–10.6, the initial species formed is the doubly reduced, doubly protonated species [Ni0(P2 PhN2 BnH)2]2+, despite a higher overpotential for this proton-coupled electron transfer reaction in comparison to forming the metal-protonated isomer. In this complex, each ligand is protonated in the exo position with the two amine moieties on each ligand binding a single proton and positioning it away from the metal center. This species undergoes very slow isomerization to form an endo-protonated hydride species [HNiII(P2 PhN2 Bn)(P2 PhN2 BnH)]2+ that can release hydrogen to close the catalytic cycle. Importantly, this slow isomerization does not perturb the initially established proton-coupled electron transfer equilibrium, placing catalysis under thermodynamic control. New details revealed about the reaction mechanism from the coupled Pourbaix diagram and the complementary stopped-flow studies lead to predictions as to how this pK a-dependent activity might be engendered in other molecular catalysts for multi-electron, multi-proton transformations.

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Section: Bnmentioning

confidence: 99%

Decoding Proton-Coupled Electron Transfer with Potential–pK_a Diagrams: Applications to Catalysis

2019

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“…70 The reactivity of these ruthenium and rhenium thioaldehyde complexes follows the expected pattern, that is nucleophilic addition at carbon and [2+4]-cycloaddition with dienes. 66,70, 71 Next we turned our attention to ruthenium complexes of a,bunsaturated thioaldehydes which were easily obtained through an acid-promoted condensation reaction (Fig. 25).…”

Section: Complexes Of Thioformaldehyde and Higher Thioaldehydesmentioning

confidence: 99%

The coordination chemistry of small sulfur-containing molecules: a personal perspective

Schenk

2011

Dalton Trans.

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The sulfur oxides SO, SO₂ and SO₃, and thioformaldehyde H₂C=S and its oxides H₂C=SO and H₂C=SO₂ form stable coordination compounds with a range of transition metals. The complexes have a rich chemistry which differs markedly from that of the free ligands. Typical reactions involve electrophilic additions, nucleophilic additions and cycloadditions. The complexes can be used as synthons to incorporate these small molecules as building blocks into larger structures.

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Metal-Carbon Bonds of Heavier Group 7 and 8 Metals (Tc, Re, Ru, Os): Mononuclear Tc/Re/Ru/Os Complexes With Metal-Carbon Bonds

Wei

Jia

2021

Comprehensive Coordination Chemistry III

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Diastereoselective Protonation, Substitution and Addition Reactions at Pseudotetrahedral Rhenium Complexes

Cited by 10 publications

References 43 publications

Decoding Proton-Coupled Electron Transfer with Potential–pK_a Diagrams: Applications to Catalysis

Decoding Proton-Coupled Electron Transfer with Potential–pK_a Diagrams: Applications to Catalysis

The coordination chemistry of small sulfur-containing molecules: a personal perspective

Metal-Carbon Bonds of Heavier Group 7 and 8 Metals (Tc, Re, Ru, Os): Mononuclear Tc/Re/Ru/Os Complexes With Metal-Carbon Bonds

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Diastereoselective Protonation, Substitution and Addition Reactions at Pseudotetrahedral Rhenium Complexes

Cited by 10 publications

References 43 publications

Decoding Proton-Coupled Electron Transfer with Potential–pKa Diagrams: Applications to Catalysis

Decoding Proton-Coupled Electron Transfer with Potential–pKa Diagrams: Applications to Catalysis

The coordination chemistry of small sulfur-containing molecules: a personal perspective

Metal-Carbon Bonds of Heavier Group 7 and 8 Metals (Tc, Re, Ru, Os): Mononuclear Tc/Re/Ru/Os Complexes With Metal-Carbon Bonds

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Decoding Proton-Coupled Electron Transfer with Potential–pK_a Diagrams: Applications to Catalysis

Decoding Proton-Coupled Electron Transfer with Potential–pK_a Diagrams: Applications to Catalysis