Alkaline Decomposition of Methyl Phenyl Phosphonium Compounds.

Aksnes, Gunnar; Brudvik, Leif J.; Lindberg, Bengt; McKay, James; Munch‐Petersen, Jon

doi:10.3891/acta.chem.scand.17-1616

Cited by 32 publications

(8 citation statements)

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“…[33] The n(PO) bands of the OPMePh 2 and OPPh 3 complexes were approximately 60 cm À1 lower in energy than the free ligands (n % 1193 cm À1 ), [34] in keeping with previous results. [29] 1 H NMR data (Table 1) confirmed the local C 1 symmetry of all species.…”

supporting

confidence: 73%

Oxygen Atom Transfer in Models for Molybdenum Enzymes: Isolation and Structural, Spectroscopic, and Computational Studies of Intermediates in Oxygen Atom Transfer from Molybdenum(VI) to Phosphorus(III)

Millar

Doonan

Smith

et al. 2005

Chemistry A European J

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Intermediates in the oxygen atom transfer from Mo(VI) to P(III), [Tp(iPr)MoOX(OPR3)] (Tp(iPr) = hydrotris(3-isopropylpyrazol-1-yl)borate; X = Cl-, phenolates, thiolates), have been isolated from the reactions of [Tp(iPr)MoO2X] with phosphines (PEt3, PMePh2, PPh3). The green, diamagnetic oxomolybdenum(IV) complexes possess local C(1) symmetry (by NMR spectroscopy) and exhibit IR bands assigned to nu(Mo==O) (approximately 950 cm(-1)) and nu(P==O) (1140-1083 cm(-1)) vibrations. The X-ray crystal structures of [Tp(iPr)MoOX(OPEt3)] (X = OC6H4-2-sBu, SnBu), [Tp(iPr)MoO(OPh)(OPMePh2)], and [Tp(iPr)MoOCl(OPPh3)] have been determined. The monomeric complexes exhibit distorted octahedral geometries, with coordination spheres composed of tridentate fac-Tp(iPr) and mutually cis monodentate terminal oxo, phosphoryl (phosphine oxide), and monoanionic X ligands. The electronic structures and stabilities of the complexes have been probed by computational methods, with the three-dimensional energy surfaces confirming the existence of a low-energy steric pocket that restricts the conformational freedom of the phosphoryl ligand and inhibits complete oxygen atom transfer. The reactivity of the complexes is also briefly described.

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supporting

confidence: 73%

Oxygen Atom Transfer in Models for Molybdenum Enzymes: Isolation and Structural, Spectroscopic, and Computational Studies of Intermediates in Oxygen Atom Transfer from Molybdenum(VI) to Phosphorus(III)

Millar

Doonan

Smith

et al. 2005

Chemistry A European J

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“…Attempts to evaluate the data in terms of the usual third-order rate law failed, Second-order kinetics have been observed only rarely in phosphonium salt hydrolysis, usually when a very stable leaving group is present, e.g. p-nitrobenzyl 33, 34 or an anionic leaving group arising from the opening of a cyclic phosphonium salt in which considerable ring-strain is pre~ent.~' It is of interest that McEwen et al 23*24 have reported that the salts 5 and 6, which also possess basic functionalities, undergo hydrolysis in accordance with the usual third-order law. The origin of the observed second-order rate law in the case of the salts 3 and 4 is not apparent although it may possibly be a consequence of an interaction between the azole nitrogen and the solvent producing a small equilibrium concentration of OH -.…”

Section: Resultsmentioning

confidence: 99%

Ligand coupling and neighbouring-group effects in the alkaline hydrolysis of arylphosphonium salts: new stable tetraarylphosphonium benzimidazolate betaines

Allen¹,

Benke²

1995

J. Chem. Soc., Perkin Trans. 1

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The reactions with aqueous alkali of a series of 2-(0-and p-triphenylphosphoniopheny1)-benzimidazoles and -benzothiazoles have been investigated. Evidence of a neighbouring-group hypervalent interaction between the pyridine-like nitrogen of the benzazole and the 2-(o-triphenylphosphoniophenyl) substituent is presented from the results of a study of the course of alkaline hydrolysis of the salts and a comparison with that of the related 2-(p-triphenylphosphoniophenyl) systems in which such hypervalent interactions are not possible. Hydrolysis of the latter proceeds abnormally, in some cases, with the formation of biaryl coupling products in addition to the expected hydrolysis products. Similar results have been obtained from a comparison of the products of hydrolysis of 0-and p-(benzoylpheny1)triphenylphosphonium salts, hydrolysis of the latter also giving rise to a biaryl coupling product, 4-benzoylbiphenyl. Traces of 4-cyanobiphenyl were also detected in the products of hydrolysis of p-cyanophenyl(tripheny1)phosphonium bromide. The kinetics of hydrolysis of the above range of salts has also been investigated in an ethanol-water solvent system (80 : 20, v/v). Whereas the benzoylphenylphosphonium salts undergo hydrolysis according to the usual third-order rate law, both series of salts derived from 1 -methyl-2-phenylbenzimidazole and 2-phenylbenzothiazole are hydrolysed according to a second-order rate law, perhaps attributable to the interaction of the azole nitrogen with the solvent. Treatment of both 2-(0-and p-triphenylphosphoniopheny1)benzimidazoles with 1 equivalent of aqueous alkali results in the formation of the related tetraarylphosphonium benzimidazolate betaines. The ortho-isomer exhibits a marked shielding of the 31P nucleus (dp -14.7) compared with the para-isomer (ap 22.6), consistent with a hypervalent interaction of the phosphonium centre with the benzimidazolate moiety. Y \ J. CHEM. SOC. PERKIN TRANS. I 1995 5 Y = H, Y' = phCH2(Ph)#+13r-6 Y = PhCH2(W)2P%I, Y' = H Paper 5/027 12H

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“…First, the decrease in rate of hydrolysis of quaternary phosphonium salts as the aliphatic character of the salt increases has been attributed to the greater electron-releasing power of the alkyl groups. Induction and hyperconjugation delocalise the positive charge on phosphorus and decrease the availability of the d orbitals which are required for the formation of the hydroxyphosphorane intermediate (2).' Second, kinetic and thermodynamic data support the view that the enhancement in rate produced by the addition of aprotic solvents is due to the desolvation of the reactants and an increase in the solvation of the hydroxyphosphorane intermediate (2).'…”

Section: Discussionmentioning

confidence: 95%

Kinetics of alkaline hydrolysis of quaternary phosphonium salts. The influence of aprotic solvents on the hydrolysis of ethyl(phenyl)phosphonium iodides

Dawber¹,

Tebby²,

Waite³

1983

J. Chem. Soc., Perkin Trans. 2

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Alkaline Decomposition of Methyl Phenyl Phosphonium Compounds.

Cited by 32 publications

References 0 publications

Oxygen Atom Transfer in Models for Molybdenum Enzymes: Isolation and Structural, Spectroscopic, and Computational Studies of Intermediates in Oxygen Atom Transfer from Molybdenum(VI) to Phosphorus(III)

Oxygen Atom Transfer in Models for Molybdenum Enzymes: Isolation and Structural, Spectroscopic, and Computational Studies of Intermediates in Oxygen Atom Transfer from Molybdenum(VI) to Phosphorus(III)

Ligand coupling and neighbouring-group effects in the alkaline hydrolysis of arylphosphonium salts: new stable tetraarylphosphonium benzimidazolate betaines

Kinetics of alkaline hydrolysis of quaternary phosphonium salts. The influence of aprotic solvents on the hydrolysis of ethyl(phenyl)phosphonium iodides

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