Rethinking the Lewis Acidity of Cationic Gallium and Indium Catalysts

Goonesinghe, Chatura; Jung, Hyuk-Joon; Betinol, Isaiah O.; Gaffen, Joshua R.; Garrard, Charley N.; Chang, Joseph; Hosseini, Kimia; Roshandel, Hootan; Nyamayaro, Kudzanai; Patrick, Brian; Ezhova, Maria; Caputo, Christopher B.; Baumgartner, Thomas; Reid, Jolene P.; Mehrkhodavandi, Parisa

doi:10.1021/acscatal.3c04918

Cited by 3 publications

(2 citation statements)

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“…As these ancillary ligands are strongly bound, they inhibit catalytic potential . With this issue identified and with a further recent report on the interesting chemistry of the heavier group 13 elements in the context of Lewis acid catalysis, we proposed the use of a related aminopyridylbisphenol ligand. In the case of metal(III) complexes of this aminopyridylbisphenol ligand, in contrast to the complexes of aminotrisphenolate, there will be a negatively charged ligand present (e.g., a halide) which helps to stabilize the complex in the same manner as the strongly coordinating ligands of the aforementioned aminotrisphenolate complex.…”

Section: Introductionmentioning

confidence: 98%

Binary and Halide-free Catalyst Systems Based on Al/Ga/In Aminopyridylbisphenolate Complexes for the Cycloaddition of Epoxides and CO₂

Damián Burgoa,

Álvarez-Miguel,

Mosquera

et al. 2024

Inorg. Chem.

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Group 13 complexes bearing an aminopyridylbisphenol ligand have been prepared [ML-X; L = ligand, M = Al (X = Cl and Br), Ga (X = Cl, Br, and I), or In (X = Cl)]. The structures of the complexes containing the chloride ligand (ML-Cl; M = Al, Ga, and In) have been directly compared through an X-ray crystallography study, with differences in the monomeric or dimeric nature of their structures observed. All of the complexes obtained have been studied as potential catalysts for the synthesis of cyclic carbonates from epoxides and CO 2 . It has been found that the indium complex, as part of a traditional binary catalyst system (catalyst + tetra-butylammonium halide cocatalyst), displays the highest catalytic activity and is active under rather mild reaction conditions (balloon pressure of CO 2 ). Meanwhile, it has been found that the GaL-I complex is a competent single-component catalyst (no need for addition of a cocatalyst) at more elevated reaction temperatures and pressures. A full substrate scope has been performed with both developed catalyst systems to demonstrate their applicability. In addition to the experimental results, a density functional theory study was performed on both catalyst systems. These results explain both why the indium catalyst is the most active under binary catalyst system conditions and how the gallium catalyst with an iodide (GaL-I) is able to act as a single-component catalyst in contrast to the indium-based complex.

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Section: Introductionmentioning

confidence: 98%

Binary and Halide-free Catalyst Systems Based on Al/Ga/In Aminopyridylbisphenolate Complexes for the Cycloaddition of Epoxides and CO₂

Damián Burgoa,

Álvarez-Miguel,

Mosquera

et al. 2024

Inorg. Chem.

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“…A number of cationic gallium complexes have been reported to be very reactive for the ROP of cyclic ethers and cyclic esters . Although the reactivity of solvent-coordinated dialkyl gallium complexes is underexplored, we hypothesized that they could offer easy access to highly active catalysts. − Intending to selectively produce high-molecular-weight poly(ether- alt -ester)s, we chose to explore the reactivity of a solvent-coordinated dialkyl gallium complex …”

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confidence: 99%

Synthesis of High-Molecular-Weight Poly(ether-alt-ester) by Selective Double Ring-Opening Polymerization of Spiroorthoesters

Jung,

Goonesinghe,

Zhang

et al. 2024

ACS Macro Lett.

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We report the selective double ring-opening polymerization of presequenced spiroorthoester monomers to form high-molecular-weight (≈90 kDa) poly(ether-alt-ester)s with a simple cationic alkyl gallium catalyst. The selective formation of double ring-opened polymer units was confirmed by NMR and IR spectroscopies. Thermal and rheological properties of homo-and copolymers were further characterized by differential scanning calorimetry, thermogravimetric analysis, and stress-controlled rotational rheometry. Linear viscoelastic moduli show that these systems are well entangled (plateau modulus), thereby possessing nearly terminal relaxation at long time scales (low frequencies) and Rouse segmental dynamics at short time scales (high frequencies) with characteristic slopes. These are the highest-molecular-weight poly(ether-alt-ester)s reported to date.

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Critical Evaluation of Childs Method for the NMR Spectroscopic Scaling of Effective Lewis Acidity: Limitations and Resolution of Earlier Discrepancies

Erdmann,

Schmitt,

Janus

et al. 2024

Chemistry A European J

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Quantifying Lewis acidity is essential for understanding and optimizing the performance of Lewis acids in diverse applications. Next to the widely accepted Gutmann‐Beckett (GB) method, using triethyl phosphine oxide (TEPO) as a probe, the Childs method—employing trans‐crotonaldehyde (TCA)—gained attention as an NMR‐based technique for measuring effective Lewis acidity (eLA). Despite its steady use, the robustness of Childs method and its correlation with other measures remain underexplored. Previous comparisons between the GB and Childs scales revealed significant discrepancies, suggesting that hard and soft acid/base (HSAB) characteristics may be operative. In this study, we compare thermodynamic data for TCA binding to 117 Lewis acids (representing global Lewis acidity, gLA) with their corresponding NMR‐induced chemical shifts in TCA. Our findings showcase notable deviations that reinforce key distinctions between eLA and gLA perspectives. Moreover, we identify significant limitations in the Childs method. First, the weak donor strength of TCA limits its applicability to only the strongest Lewis acids. Second, the exposed protons of TCA are prone to secondary interactions, obscuring the measurement of true Lewis acidity. Finally, our analysis reconciles discrepancies, refuting earlier assumptions that these arise from HSAB effects.

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Rethinking the Lewis Acidity of Cationic Gallium and Indium Catalysts

Cited by 3 publications

References 50 publications

Binary and Halide-free Catalyst Systems Based on Al/Ga/In Aminopyridylbisphenolate Complexes for the Cycloaddition of Epoxides and CO₂

Binary and Halide-free Catalyst Systems Based on Al/Ga/In Aminopyridylbisphenolate Complexes for the Cycloaddition of Epoxides and CO₂

Synthesis of High-Molecular-Weight Poly(ether-alt-ester) by Selective Double Ring-Opening Polymerization of Spiroorthoesters

Critical Evaluation of Childs Method for the NMR Spectroscopic Scaling of Effective Lewis Acidity: Limitations and Resolution of Earlier Discrepancies

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Rethinking the Lewis Acidity of Cationic Gallium and Indium Catalysts

Cited by 3 publications

References 50 publications

Binary and Halide-free Catalyst Systems Based on Al/Ga/In Aminopyridylbisphenolate Complexes for the Cycloaddition of Epoxides and CO2

Binary and Halide-free Catalyst Systems Based on Al/Ga/In Aminopyridylbisphenolate Complexes for the Cycloaddition of Epoxides and CO2

Synthesis of High-Molecular-Weight Poly(ether-alt-ester) by Selective Double Ring-Opening Polymerization of Spiroorthoesters

Critical Evaluation of Childs Method for the NMR Spectroscopic Scaling of Effective Lewis Acidity: Limitations and Resolution of Earlier Discrepancies

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Product

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Binary and Halide-free Catalyst Systems Based on Al/Ga/In Aminopyridylbisphenolate Complexes for the Cycloaddition of Epoxides and CO₂

Binary and Halide-free Catalyst Systems Based on Al/Ga/In Aminopyridylbisphenolate Complexes for the Cycloaddition of Epoxides and CO₂