A reusable apparatus for the convenient determination of the molecular weight of air- or moisture-sensitive compounds

Zoellner, Robert W.

doi:10.1021/ed067p714

Cited by 23 publications

(22 citation statements)

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“…18 Interestingly, the double hapticity of the nitriles has been observed with only select transition metals, 17a and to the best of our knowledge, has only been observed for nickel in tetranuclear species. 17 Importantly, Signer analysis 19 confirmed that 3a exists as a dimer in solution (MW = cald. 978.7; obsd 961.9 ± 100) as well as the solid state.…”

Section: Resultsmentioning

confidence: 91%

The Discovery of [Ni(NHC)RCN]₂ Species and Their Role as Cycloaddition Catalysts for the Formation of Pyridines

et al. 2012

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The reaction of Ni(COD)2, IPr, and nitrile affords dimeric [Ni(IPr)RCN]2 in high yields. X-ray analysis revealed these species display simultaneous η1- and η2-nitrile binding modes. These dimers are catalytically competent in the formation of pyridines from the cycloaddition of diynes and nitriles. Kinetic analysis showed the reaction to be first order in [Ni(IPr)RCN]2, zeroth order in added IPr, zeroth order in nitrile, and zeroth order in diyne. Extensive stoichiometric competition studies were performed, and selective incorporation of the exogenous, not dimer bound, nitrile was observed. Post cycloaddition, the dimeric state was found to be largely preserved. Nitrile and ligand exchange experiments were performed and found to be inoperative in the catalytic cycle. These observations suggest a mechanism whereby the catalyst is activated by partial dimer-opening followed by binding of exogenous nitrile and subsequent oxidative heterocoupling.

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Section: Resultsmentioning

confidence: 91%

The Discovery of [Ni(NHC)RCN]₂ Species and Their Role as Cycloaddition Catalysts for the Formation of Pyridines

et al. 2012

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“…The molecular weight determined by the Signer method was 717 g/mol in CH 3 OH at 24 °C. Although this measured value is lower than that for complex 36 (872 g/mol), it is clearly smaller than that expected for higher aggregates of 36 and larger than values for potential mononuclear silver compounds (e.g., 466 g/mol for LAgCO 3 H, L = JohnPhos).…”

Section: Resultsmentioning

confidence: 98%

Site-Selective Silver-Catalyzed C–H Bond Deuteration of Five-Membered Aromatic Heterocycles and Pharmaceuticals

Tlahuext‐Aca

Hartwig

2021

ACS Catal.

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Catalytic methods for the direct introduction of hydrogen isotopes into organic molecules are essential to the development of improved pharmaceuticals and to the alteration of their absorption, distribution, metabolism, and excretion (ADME) properties. However, the development of homogeneous catalysts for selective incorporation of isotopes in the absence of directing groups under practical conditions remains a long-standing challenge. Here, we show that a phosphine-ligated, silver-carbonate complex catalyzes the site-selective deuteration of C–H bonds in five-membered aromatic heterocycles and active pharmaceutical ingredients that have been resistant to catalytic H/D exchange. The reactions occur with CH3OD as a low-cost source of the isotope. The silver catalysts react with five-membered heteroarenes lacking directing groups, tolerate a wide range of functional groups, and react in both polar and nonpolar solvents. Mechanistic experiments, including deuterium kinetic isotope effects, determination of kinetic orders, and identification of the catalyst resting state, support C–H bond cleavage from a phosphine-ligated, silver-carbonate intermediate as the rate-determining step of the catalytic cycle.

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“…The products were isolated from cold (−30 °C) pentane as yelloworange crystals in high yield (82% for 1 and 76% for 2); however, attempts to obtain X-ray quality crystals for structure analysis have so far proven futile. Both 1 and 2 are dimeric in benzene solution (by the Signer method 16 ). These electron-rich Rh(I) compounds are air-and moisture-sensitive.…”

Section: Synthesis Of the Molecular Precursors {(Diene)rh[-osi-(o T ...mentioning

confidence: 99%

Synthesis and characterization of {(diene)Rh[μ-OSi(O^tBu)₃]}₂, a precursor to silica-bound rhodium

Jarupatrakorn

Tilley

2004

Dalton Trans.

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Reaction of [(diene)RhCl]2 with 2 equiv of KOSi(OtBu)3 afforded [(diene)Rh[mu-OSi(OtBu)3]]2, where diene=cod (1) and nbd (2). Multinuclear NMR studies reveal that 1 and 2 have a dimeric structure with bridging tris(tert-butoxy)siloxy ligands. These dimers are folded along the O...O axis. Complexes and reacted with PR3(R=Me, Ph) to give monomeric products, the formulae of which depend on the amount of PR3 added ((diene)Rh[OSi(OtBu)3](PR3) and Rh[OSi(OtBu)3](PMe3)3). The behavior of 1 towards water and methanol is discussed. Thermogravimetric analyses (TGAs) of 1 and 2 reveal rather sharp conversions to rhodium-containing materials. Thermolysis of 1 in toluene at 180 degrees C resulted in formation of a black precipitate, which contained rhodium nanoparticles with an average diameter of 22 nm, as determined by powder X-ray diffraction (PXRD), after calcination at 300 degrees C for 1 h.

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A reusable apparatus for the convenient determination of the molecular weight of air- or moisture-sensitive compounds

Abstract: Construction and application of an apparatus for the determination of the apparent molecular weight of air- or moisture sensitive compounds employing Singer's method of isothermal distillation.

Cited by 23 publications

References 0 publications

The Discovery of [Ni(NHC)RCN]₂ Species and Their Role as Cycloaddition Catalysts for the Formation of Pyridines

The Discovery of [Ni(NHC)RCN]₂ Species and Their Role as Cycloaddition Catalysts for the Formation of Pyridines

Site-Selective Silver-Catalyzed C–H Bond Deuteration of Five-Membered Aromatic Heterocycles and Pharmaceuticals

Synthesis and characterization of {(diene)Rh[μ-OSi(O^tBu)₃]}₂, a precursor to silica-bound rhodium

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A reusable apparatus for the convenient determination of the molecular weight of air- or moisture-sensitive compounds

Abstract: Construction and application of an apparatus for the determination of the apparent molecular weight of air- or moisture sensitive compounds employing Singer's method of isothermal distillation.

Cited by 23 publications

References 0 publications

The Discovery of [Ni(NHC)RCN]2 Species and Their Role as Cycloaddition Catalysts for the Formation of Pyridines

The Discovery of [Ni(NHC)RCN]2 Species and Their Role as Cycloaddition Catalysts for the Formation of Pyridines

Site-Selective Silver-Catalyzed C–H Bond Deuteration of Five-Membered Aromatic Heterocycles and Pharmaceuticals

Synthesis and characterization of {(diene)Rh[μ-OSi(OtBu)3]}2, a precursor to silica-bound rhodium

Contact Info

Product

Resources

About

The Discovery of [Ni(NHC)RCN]₂ Species and Their Role as Cycloaddition Catalysts for the Formation of Pyridines

The Discovery of [Ni(NHC)RCN]₂ Species and Their Role as Cycloaddition Catalysts for the Formation of Pyridines

Synthesis and characterization of {(diene)Rh[μ-OSi(O^tBu)₃]}₂, a precursor to silica-bound rhodium