Metal‐coordinated Hydroxide as a Nucleophile: a Brief History

Blackman, Allan G.; Gahan, Lawrence R.

doi:10.1002/zaac.201800045

Cited by 10 publications

(4 citation statements)

References 270 publications

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“…The lack of oxygen atoms in 1 and NH 3 clearly shows that the source of oxygen impurities is not precursor-related. The sources could include residual oxygen and moisture in the ALD reaction chamber, etching of the inductively coupled plasma quartz tube, or post-deposition oxidation of GaN films (GaN, Δ f G ° = −78 kJ/mol –1 ; Ga 2 O 3 , Δ f G ° = −998 kJ/mol –1 ) . The higher tolerance of 1 to oxygen and moisture over GaMe 3 and Ga(NMe 2 ) 3 gives great promise to completely removing the oxygen impurities.…”

Section: Resultsmentioning

confidence: 99%

Hexacoordinated Gallium(III) Triazenide Precursor for Epitaxial Gallium Nitride by Atomic Layer Deposition

et al. 2021

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Gallium nitride (GaN) is the main component of modern-day high electron mobility transistors due to its favorable electronic properties. As electronic devices become smaller with more complex surface architecture, the ability to deposit high-quality GaN films at low temperatures is required. Herein, we report a new highly volatile Ga(III) triazenide precursor and demonstrate its ability to deposit high-quality epitaxial GaN by atomic layer deposition (ALD). This new Ga(III) triazenide, the first hexacoordinated Ga−N bonded precursor used in a vapor deposition process, was easily synthesized and purified by either sublimation or recrystallisation. Thermogravimetric analysis showed single-step volatilization with an onset temperature of 155 °C and negligible residual mass. Three temperature intervals with self-limiting growth were observed when depositing GaN films. The GaN films grown in the second growth interval at 350 °C were epitaxial on 4H−SiC without an AlN seed layer and found to have a near stoichiometric Ga/N ratio with very low levels of impurities. In addition, electron microstructure analysis showed a smooth film surface and a sharp interface between the substrate and film. The band gap of these films was 3.41 eV with the Fermi level at 1.90 eV, showing that the GaN films were unintentionally n-type-doped. This new triazenide precursor enables ALD of GaN for semiconductor applications and provides a new Ga(III) precursor for future deposition processes.

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Section: Resultsmentioning

confidence: 99%

Hexacoordinated Gallium(III) Triazenide Precursor for Epitaxial Gallium Nitride by Atomic Layer Deposition

et al. 2021

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“…The pH optima vary from 7.8 to 11, with one example having a maximum at pH 6. Common to all of these systems is that the active species is a metal‐bound hydroxido (M−OH) nucleophile, [102] analogous to the majority of known homogeneous counterparts [28, 32, 44–50, 103, 104] …”

Section: Catalytic Activitymentioning

confidence: 99%

“…The pH optima vary from 7.8 to 11,w ith one example having amaximum at pH 6. Common to all of these systems is that the actives peciesi sametal-bound hydroxido (MÀOH) nucleophile, [102] analogous to the majority of known homogeneous counterparts. [28, 32, 44-50, 103, 104] The substrates employed are typically "activated" phosphate esters:c ommon examples include 2,4-DNPP,2 ,4-BDNPP,4 -BNPP,4 -NPP,a nd HPNPP and those less commonly employed are ENPMP,E 3,5DCPMPT, and H3,5DCPMPT ( Tables 1a nd 2).…”

Section: Catalytic Activitymentioning

confidence: 99%

Recent Advances in Heterogeneous Catalytic Systems Containing Metal Ions for Phosphate Ester Hydrolysis

Gomes

Fernandes

Gahan

et al. 2020

Chemistry A European J

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Organophosphates are a class of organic compounds that are important for living organisms, forming the building blocks for DNA, RNA, and some essential cofactors. Furthermore, non‐natural organophosphates are widely used in industrial applications, including as pesticides; in laundry detergents; and, unfortunately, as chemical weapons agents. In some cases, the natural degradation of organophosphates can take thousands of years; this longevity creates problems associated with handling and the storage of waste generated by such phosphate esters, in particular. Efforts to develop new catalysts for the cleavage of phosphate esters have progressed in recent decades, mainly in the area of homogeneous catalysis. In contrast, the development of heterogeneous catalysts for the hydrolysis of organophosphates has not been as prominent. Herein, examples of heterogeneous systems are described and the importance of the development of heterogeneous catalysts applicable to organophosphate hydrolysis is highlighted, shedding light on recent advances related to different solid matrices that have been employed.

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“…Species containing such reactive M−OH, M−OR or M−NR 2 linkages are key intermediates in various catalytic processes, ranging from commodity industrial processes (like the Wacker reaction) [6] to biocatalysis, e. g. in metalloenzymes like carbonic anhydrase or alcohol deshydrogenase [7] . Furthermore, the nucleophilicity of covalent metal hydroxides played an important role in the historic development Coordination Chemistry [8] . In contrast with the usually well‐defined nature of M−C bonds, the chemistry of M−OH or M−OR ensembles is often complicated by their tendency to cancel its basicity forming multinuclear aggregates, to experience irreversible hydrogen elimination processes, or simply by their facile hydrolysis with the slightest moisture traces.…”

Section: Introductionmentioning

confidence: 99%

Nucleophilic Nickel and Palladium Pincer Hydroxides: A Study of Their Reactions with Dimethyl Carbonate and Other Non‐Alkylating Organic Electrophiles

et al. 2021

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The reactions of the pincer hydroxide complexes [(iPrPCP)M(OH)] (M=Ni, Pd) with dimethyl carbonate (DMC), and a set of organic electrophiles including benzaldehyde have been investigated in the context of our ongoing investigation on the synthesis of alkyl carbonates from CO2 and alcohols. The final outcome of such reactions is diverse, but for PhCHO and DMC the first step is a mechanistically similar addition of the [M]−OH linkage across the carbonyl functionality, that leads to unstable adducts. DMC is cleaved irreversibly by both Ni and Pd hydroxides, affording the corresponding methylcarbonates [(iPrPCP)MOCO2Me] and methanol, whereas PhCHO affords benzoate complexes [[(iPrPCP)MOCO2Ph]. The main kinetic and thermodynamic features of these reactions were reproduced satisfactorily by computational DFT models. The calculations throw light on the true causes of irreversibility of DMC cleavage by nucleophilic hydroxide complexes, which is the primary cause that prevents methanol carboxylation from being catalysed by the Ni or Pd pincers.

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Metal‐coordinated Hydroxide as a Nucleophile: a Brief History

Cited by 10 publications

References 270 publications

Hexacoordinated Gallium(III) Triazenide Precursor for Epitaxial Gallium Nitride by Atomic Layer Deposition

Hexacoordinated Gallium(III) Triazenide Precursor for Epitaxial Gallium Nitride by Atomic Layer Deposition

Recent Advances in Heterogeneous Catalytic Systems Containing Metal Ions for Phosphate Ester Hydrolysis

Nucleophilic Nickel and Palladium Pincer Hydroxides: A Study of Their Reactions with Dimethyl Carbonate and Other Non‐Alkylating Organic Electrophiles

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