Group 10 Metal–Metal Bonds

Lu, Erli; Liddle, Stephen T.

doi:10.1002/9783527673353.ch10

Cited by 11 publications

(20 citation statements)

References 168 publications

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“…In particular, the nature of the metal−metal interaction in Pd III 2 remains unknown. Whereas many Pd III 2 complexes 23,24 contain direct Pd−Pd bonds, the Pd centers can also be linked through one or more bridging ligands. 25,26 Furthermore, most metal−metal bonded Pd III 2 complexes are obtained via oxidation of cofacially oriented, ligand-bridged, dinuclear Pd II 2 complexes in which the Pd centers are predisposed toward facile M−M bond formation using two-electron chemical oxidants.…”

Section: ■ Introductionmentioning

confidence: 99%

“…In particular, the nature of the metal–metal interaction in Pd III 2 remains unknown. Whereas many Pd III 2 complexes , contain direct Pd–Pd bonds, the Pd centers can also be linked through one or more bridging ligands. , Furthermore, most metal–metal bonded Pd III 2 complexes are obtained via oxidation of cofacially oriented, ligand-bridged, dinuclear Pd II 2 complexes in which the Pd centers are predisposed toward facile M–M bond formation using two-electron chemical oxidants. In contrast, our Pd III 2 complex is generated via sequential one-electron electrochemical oxidation from a simple mononuclear Pd II (sulfate) complex, leaving open the critical questions of whether a M–M bond exists in the Pd III 2 species and what role it plays in fostering the unusual ECE electrochemical oxidation mechanism.…”

Section: Introductionmentioning

confidence: 99%

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Rapid Electrochemical Methane Functionalization Involves Pd–Pd Bonded Intermediates

et al. 2020

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High-valent Pd complexes are potent agents for the oxidative functionalization of inert C–H bonds, and it was previously shown that rapid electrocatalytic methane monofunctionalization could be achieved by electro-oxidation of PdII to a critical dinuclear PdIII intermediate in concentrated or fuming sulfuric acid. However, the structure of this highly reactive, unisolable intermediate, as well as the structural basis for its mechanism of electrochemical formation, remained elusive. Herein, we use X-ray absorption and Raman spectroscopies to assemble a structural model of the potent methane-activating intermediate as a PdIII dimer with a Pd–Pd bond and a 5-fold O atom coordination by HxSO4 (x–2) ligands at each Pd center. We further use EPR spectroscopy to identify a mixed-valent M–M bonded Pd2 II,III species as a key intermediate during the PdII-to-PdIII 2 oxidation. Combining EPR and electrochemical data, we quantify the free energy of Pd dimerization as <−4.5 kcal/mol for Pd2 II,III and <−9.1 kcal/mol for PdIII 2. The structural and thermochemical data suggest that the aggregate effect of metal–metal and axial metal–ligand bond formation drives the critical Pd dimerization reaction in between electrochemical oxidation steps. This work establishes a structural basis for the facile electrochemical oxidation of PdII to a M–M bonded PdIII dimer and provides a foundation for understanding its rapid methane functionalization reactivity.

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Section: ■ Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Rapid Electrochemical Methane Functionalization Involves Pd–Pd Bonded Intermediates

et al. 2020

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“…The Pd–Pd distance of 2.4764(7) Å is consistent with the presence of a bond between the two metals. [15] The 78.04(4)° dihedral angle between the planes of the two coordinated DAF ligands presumably allows Pd–N bonding to be maximized while allowing the Pd centers to optimize Pd–Pd bonding. The acetate ligands exhibit a syn relationship, in which the carbonyl groups are oriented in the same direction.…”

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confidence: 99%

Detection of Palladium(I) in Aerobic Oxidation Catalysis

et al. 2017

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PdII-catalyzed oxidation reactions exhibit broad utility in organic synthesis; however, they often feature high catalyst loading and low turnover numbers relative to non-oxidative cross-coupling reactions. Insights into the fate of the Pd catalyst during turnover could help to address this limitation. Here, we report the identification and characterization of a dimeric PdI species in two prototypical Pd-catalyzed aerobic oxidation reactions: allylic C–H acetoxylation of terminal alkenes and intramolecular aza-Wacker cyclization. Both reactions employ 4,5-diazafluoren-9-one (DAF) as an ancillary ligand. The dimeric PdI complex, [PdI(μ-DAF)(OAc)]2, which features two bridging DAF ligands and two terminal acetate ligands, has been characterized by several spectroscopic methods, as well as single-crystal X-ray crystallography. The origin of this PdI complex and its implications for catalytic reactivity are discussed.

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“…Ultimately we used density functional theory (DFT) to model complex α . Calculations converged toward a complex displaying a 2.90-Å-long Pd II –Cu I contact, a length typical of group 10/group 11 heterobimetallic complexes involving a Pd II . The Pd II atom is square planar, while the Cu I atom shows a trigonal planar geometry with an additional apical bonding with Pd II .…”

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confidence: 92%

Stereoselective Access to (E)-1,3-Enynes through Pd/Cu-Catalyzed Alkyne Hydrocarbation of Allenes

et al. 2019

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PdII and CuI cooperate in catalyzing the alkynes hydrocarbation of allenes (AHA) giving (E)-1,3-enynes with high yields, atom economy, and high regio-/stereoselectivities. We devised new efficient conditions and expanded the substrate scope. Experimental and computational studies support a nonorthodox PdII/PdIV catalytic cycle involving an oxidative addition triggered by a stereodeterminant H+ transfer. This reaction is leveraged in a new strategy of stereoselective synthesis of 1,3-dienes.

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Group 10 Metal–Metal Bonds

Cited by 11 publications

References 168 publications

Rapid Electrochemical Methane Functionalization Involves Pd–Pd Bonded Intermediates

Rapid Electrochemical Methane Functionalization Involves Pd–Pd Bonded Intermediates

Detection of Palladium(I) in Aerobic Oxidation Catalysis

Stereoselective Access to (E)-1,3-Enynes through Pd/Cu-Catalyzed Alkyne Hydrocarbation of Allenes

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