Changes in ligand coordination mode induce bimetallic C–C coupling pathways

Jackman, Kyle M K; Liang, Guangchao; Boyle, Paul D.; Zimmerman, Paul M.; Blacquiere, Johanna M.

doi:10.1039/d2dt00322h

Cited by 3 publications

(2 citation statements)

References 63 publications

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“…23 We have previously reported the synthesis and coordination chemistry of a ligand [Ph 2 P(C 6 H 4 )NCHC(CH 3 ) 2 ] − (L1) bearing phosphine and 1-azaallyl donor groups. [24][25][26] This ligand exhibits a broad range of coordination modes that depend on the metal, metal oxidation state, and the presence of additional L-donor ligands. In the presence of pyridine, a κ 2 -P,N mode was enforced to give coordinatively saturated Ru(II) or Pd(II) complexes (F and G, respectively).…”

Section: Introductionmentioning

confidence: 99%

“…24,25 In the absence of pyridine, Pd(II) is stabilized by a µ-N bridging mode in H. 25 This Pd complex undergoes reductive elimination in which C-C bond formation is promoted by the capacity of L1 to access and switch between different coordination modes. 25,26 Reductive elimination forms a Pd(I) dimer I that is supported by a different bridging mode of the 1-azaallyl group. Notably, even in the absence of a donor ligand, the η 3 -NCC coordination mode of the 1-azaallyl group of L1 was not observed with Ru or Pd complexes.…”

Section: Introductionmentioning

confidence: 99%

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Operationally unsaturated ruthenium complex stabilized by a phosphine 1-azaallyl ligand

Kindervater,

Staroverov,

Jackman

et al. 2023

Dalton Trans.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Operationally unsaturated ruthenium complex stabilized by a phosphine 1-azaallyl ligand

Kindervater,

Staroverov,

Jackman

et al. 2023

Dalton Trans.

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Shapeshifting Ligands Mask Lewis Acidity of Dicationic Palladium(II)

Sipps,

Gibbs,

Sayfutyarova

et al. 2024

ACS Catal.

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Supporting ligands limit the degree of electrophilic activation for any substrate because they also reduce the Lewis acidity of the transition metal ion. Here, we temporarily mask the Lewis acidity of dicationic Pd(II) by using "shapeshifting" bidentate pyrimidine/olefin ligands L1 and L2. These ligands delocalize/relocalize charge via reversible C−N bond formation. So, although ligated dicationic Pd compounds [1] 2+ and [2] 2+ appear charge separated (distributed across Pd and ligand), they react comparably to a solvated Pd(II) dication. Despite reacting like strong Lewis acids, the complexes are tolerant of polar functional groups (Lewis bases that often inhibit electrophilic catalysis). We propose that this property originates from the installation of a more nucleophilic (charge separated) state. This case study suggests that catalysts featuring reversible dynamics can be advantageous relative to their structurally static counterparts.

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Structural Study of Model Rhodium(I) Carbonylation Catalysts Activated by Indole-2-/Indoline-2-Carboxylate Bidentate Ligands and Kinetics of Iodomethane Oxidative Addition

et al. 2022

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The rigid-backbone bidentate ligands Indoline-2-carboxylic acid (IndoliH) and Indole-2-carboxylic acid (IndolH) were evaluated for rhodium(I). IndoliH formed [Rh(Indoli)(CO)(PPh3)] (A2), while IndolH yielded the novel dinuclear [Rh1(Indol’)(CO)(PPh3)Rh2(CO)(PPh3)2] (B2) complex (Indol’ = Indol2−), which were characterized by SCXRD. In B2, the Rh1(I) fragment [Rh1(Indol’)(CO)(PPh3)] (bidentate N,O-Indol) exhibits a square-planar geometry, while Rh2(I) shows a ‘Vaska’-type trans-[O-Rh2(PPh3)2(CO)] configuration (bridging the carboxylate ‘oxo’ O atom of Indol2−). The oxidative addition of MeI to A2 and B2 via time-resolved FT-IR, NMR, and UV/Vis analyses indicated only Rh(III)-alkyl species (A3/B3) as products (no migratory insertion). Variable temperature kinetics confirmed an associative mechanism for A2 via an equilibrium-based pathway (ΔH≠ = (21 ± 1) kJ mol−1; ΔS≠ = (−209 ± 4) J K−1mol−1), with a smaller contribution from a reverse reductive elimination/solvent pathway. The dinuclear complex B2 showed the oxidative addition of MeI only at Rh1(I), which formed a Rh(III)-alkyl, but cleaved the bridged Rh2(I) site, yielding trans-[RhI(PPh3)2(I)(CO)] (5B) as a secondary product. A significantly smaller negative activation entropy [ΔH≠ = (73.0 ± 1.2) kJ mol−1; ΔS≠ = (−21 ± 4) J K−1mol−1] via a more complex/potential interchange mechanism (the contribution of ΔS≠ to the Gibbs free energy of activation, ΔG≠, only ±10%) was inferred, contrary to the entropy-driven oxidative addition of MeI to A2 (the contribution of ΔS≠ to ΔG≠ ± 75%).

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Changes in ligand coordination mode induce bimetallic C–C coupling pathways

Abstract: Ligand L1 with a 1-azaallyl group undergoes reversible changes in coordination mode in response to the demands of the metal, which enables bimetallic C–C reductive elimination pathways.

Cited by 3 publications

References 63 publications

Operationally unsaturated ruthenium complex stabilized by a phosphine 1-azaallyl ligand

Operationally unsaturated ruthenium complex stabilized by a phosphine 1-azaallyl ligand

Shapeshifting Ligands Mask Lewis Acidity of Dicationic Palladium(II)

Structural Study of Model Rhodium(I) Carbonylation Catalysts Activated by Indole-2-/Indoline-2-Carboxylate Bidentate Ligands and Kinetics of Iodomethane Oxidative Addition

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