Evaluation of the Lewis acidity of metal complexes using ESI mass spectrometry

Zhang, Rong; Li, Pingping; Gu, Ge‐Ge; Ren, Wei‐Min

doi:10.1177/1469066720944330

Cited by 5 publications

(4 citation statements)

References 64 publications

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“…We also observed a product ion at m / z 296.9 assigned to the reductive elimination of the charge-tagged aryl halide [IC 6 H 4 CH 2 SO 3 ] − (Figure a). Additionally, detection of the Pd II product ion [Ph 2 P(C 6 H 4 CH 2 SO 3 )] − indicates the occurrence of intramolecular aryl-phosphine scrambling (Figure a, green), a known side reaction in palladium-catalyzed cross-coupling reactions, − often leading to undesired scrambled side products and catalyst deactivation. − Our results suggest that the scrambling process is facile , and can be easily initiated under energetic CID conditions (see Figures S9 and S10 for more details) …”

Section: Resultsmentioning

confidence: 80%

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Poisonous Truth about the Mercury Drop Test: The Effect of Elemental Mercury on Pd(0) and Pd(II)ArX Intermediates

Chagunda,

Fisher,

Schierling

et al. 2023

Organometallics

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The mercury drop test is a widely used method often regarded as decisive for discriminating between homogeneous and heterogeneous catalysis in organometallic systems. However, recent research has highlighted the limitations of this test due to the intrinsic reactivity of some organometallic compounds toward elemental mercury. In this study, we used real-time mass spectrometry to investigate the effect of elemental mercury on L n Pd 0 and Pd II ArX intermediates common in palladium-catalyzed cross-coupling reactions. Our findings demonstrate that mercury can interact with both species through redox-transmetallation and amalgamation processes, leading to inhibition of catalytic activity, which would often be misinterpreted as evidence for heterogeneous catalysis. This result further calls into question the widely held assumption that mercury reacts selectively with heterogeneous catalytic species. Therefore, it is important to carefully evaluate the results provided by the mercury drop test and incorporate alternative comprehensive kinetic analysis of the catalyst.

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Section: Resultsmentioning

confidence: 80%

“…60−62 Our results suggest that the scrambling process is facile 40,63 and can be easily initiated under energetic CID conditions (see Figures S9 and S10 for more details). 73 The Hg II abundance (Figure 5b). This product ion, as well as I − , results from the homolytic cleavage of the X-type ligands.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

Poisonous Truth about the Mercury Drop Test: The Effect of Elemental Mercury on Pd(0) and Pd(II)ArX Intermediates

Chagunda,

Fisher,

Schierling

et al. 2023

Organometallics

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show abstract

“…These findings provide insight into the characteristics of Pd II and Hg II transmetallation intermediates and can be used to diagnose substrate binding strength and composition. [91][92][93][94]…”

Section: Investigation Of Pd/hg Redox-transmetallationmentioning

confidence: 99%

The poisonous truth about the mercury drop test: the effect of elemental mercury on Pd(0) and Pd(II)ArX intermediates

Chagunda,

Fisher,

Schierling

et al. 2023

Preprint

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The mercury drop test is a widely used method for distinguishing between homogeneous and heterogeneous catalysis in organometallic systems. However, recent research has highlighted the limitations of this test due to the intrinsic reactivity of some organometallic compounds towards elemental mercury. In this study, we used real-time mass spectrometry with charge-tagged substrates to investigate the effect of elemental mercury on LnPd0 and PdIIArX intermediates common in palladium-catalysed cross-coupling reactions. Our findings demonstrate that mercury can interact with both species through redox-transmetallation and amalgamation processes, leading to a decrease in catalytic activity. This result further calls into question the fundamental assumption of mercury selectivity towards heterogeneous catalytic species. These results highlight the importance of careful consideration of the results the mercury drop test provides and encourages further research to gain a more comprehensive understanding of catalyst poisoning mechanisms.

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“…Whereas both Co. and Cr catalysts are active in epoxide/ CO 2 copolymerization and Al catalysts are active in epoxide/ anhydride copolymerization (Longo et al, 2016), only Cr catalysts were active in epoxide/CS 2 copolymerization. It is expected that the combined Lewis acidity, oxophilicity, and thiophilicity of Cr are key thermodynamic considerations for promoting catalyst activity in both propagation and O-S exchange mechanisms (Kepp, 2016;Zhang et al, 2020).…”

Section: Epoxide/cs 2 Copolymerizationmentioning

confidence: 99%

Metal-catalyzed copolymerizations of epoxides and carbon disulfide for high-refractive index low absorbance adhesives and plastics

Schwarz,

Patil,

Singla

et al. 2023

Front. Chem.

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High-refractive index plastics are useful materials due to their optical properties, ease of processing, and low-costs compared to their inorganic counterparts. Catalytic carbon disulfide (CS2) copolymerization with epoxides is one method for producing low-cost high refractive index polymers. The reaction is accompanied by an oxygen-sulfur exchange reaction which produces irregular microstructures in the repeating units. In this study, metal salen catalysts were investigated with different metal centers (Al, Cr, Co) and salen ligand electronics, sterics, backbones, and co-catalyst in the copolymerization of CS2 with propylene oxide (PO) and cyclohexene oxide (CHO). The results reveal the essential nature of Cr metal centers on reactivity and the backbone geometry on monomer selectivity. There were no significant impacts on the O-S exchange reaction when ligand design changed, however PO and CHO/CS2 copolymers yield different monothiocarbonate microstructures. Additionally, the effects of microstructure on optical and thermal properties were investigated using spectroscopic ellipsometry and calorimetry, respectively. The CHO system produced high Tg plastics (93°C) with high refractive indexes (n up to 1.64), modest absorbance (κ < 0.020), and Abbe numbers of 32.2 while PO yielded low Tg adhesives (Tg = 9°C) with high refractive indexes (n up to 1.73), low absorbance (κ < 0.005), and low Abbe numbers (VD = 19.1).

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Evaluation of the Lewis acidity of metal complexes using ESI mass spectrometry

Cited by 5 publications

References 64 publications

Poisonous Truth about the Mercury Drop Test: The Effect of Elemental Mercury on Pd(0) and Pd(II)ArX Intermediates

Poisonous Truth about the Mercury Drop Test: The Effect of Elemental Mercury on Pd(0) and Pd(II)ArX Intermediates

The poisonous truth about the mercury drop test: the effect of elemental mercury on Pd(0) and Pd(II)ArX intermediates

Metal-catalyzed copolymerizations of epoxides and carbon disulfide for high-refractive index low absorbance adhesives and plastics

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