Kinetics and mechanisms of the formation, acid-catalyzed decomposition and intramolecular isomerization of oxygen-bonded (sulfito)pentaaquochromium(III) perchlorate

Moritzen, P. A.; El-Awady, Abbas A.; Harris, G. M.

doi:10.1021/ic00197a015

Cited by 15 publications

(7 citation statements)

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“…3+ respectively at 25°C and I = 1⋅0 mol dm -3 ). 9,22 This is in conformity with Bronstead catalysis law which has been found to be valid for SO 2 uptake reactions of metal-hydroxo species. 12c This work further shows that the reaction of Rh(OH 2 ) 6 3+ with SO 2 is statistically insignificant (k 2 = 0⋅002 ± 5⋅3 dm 3 mol -1 s -1 at 25°C, see table 1).…”

Section: +supporting

confidence: 87%

“…It is interesting to note that the SO 2 uptake rate constant (k 1 ) for Rh(OH 2 ) 5 OH 2+ is 10 5 times smaller than the same for Rh(NH 3 ) 5 OH 2+ (k 1 = 1⋅8 × 10 8 dm 3 mol -1 s -1 at 25°C, I = 1⋅0 mol dm -3 ) 9 but comparable to that of Cr(OH 2 ) 5 OH 2+ (k 1 = 4⋅4 × 10 2 dm 3 mol -1 s -1 at 25°C, I = 1⋅0 mol dm -3 ). 22 The k 1 values parallel the basicity of the M-OH 2+ species as adjudged by the pK of the corresponding aqua cations (pK 3 = 6⋅8 and 3⋅88 for (NH 3 ) 5 RhOH 2…”

Section: +mentioning

confidence: 85%

“…8, 23,25 The [Pt(NH 3 ) 4 (OH 2 )(OSO 2 )] 2+ is reported to isomerise to its S-bonded analogue with k iso = 4⋅0 × 10 -5 s -1 (25°C). 26 Moritzen et al 22 reported a value of 2 × 10 -4 s -1 (25°C) for Cr(OH 2 ) 5 (OSO 2 ) + . Since S-sulphite is a soft ligand and Cr(OH 2 ) 6 3+ is a hard metal ion, the ligand isomerisation in this system is less likely.…”

Section: Rh(oh 2 ) 5 (-Osomentioning

confidence: 99%

“…23 The relevant data for other protonated O-sulphito complexes are not available for comparison. Moritzen et al 22 did not observe significant protonation of Cr(OH 2 ) 5 (OSO 2 ) + (0⋅15 < [H + ] < 1⋅0 mol dm -3 ) and reported the second order rate constant for SO 2 elimination as 1⋅58 ± 0⋅04 dm 3 mol -1 s -1 (25°C, I = 1⋅0 mol dm -3 ).…”

Section: +mentioning

confidence: 99%

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Kinetics and mechanism of the reactions of hexaaqua rhodium (III) with sulphur (IV) in aqueous medium

Nayak

Dash

2004

J Chem Sci

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An O-bonded sulphito complex, Rh(OH 2) 5 (OSO 2 H) 2+ , is reversibly formed in the stoppedflow time scale when Rh(OH 2) 6 3+ and SO 2 /HSO 3 buffer (1 < pH < 3) are allowed to react. For Rh(OH 2) 5 OH 2+ + SO 2 Rh(OH 2) 5 (OSO 2 H) 2+ (k 1 /k-1), k 1 = (2⋅2 ± 0⋅2) × 10 3 dm 3 mol-1 s-1 , k-1 = 0⋅58 ± 0⋅16 s-1 (25°C, I = 0⋅5 mol dm-3). The protonated O-sulphito complex is a moderate acid (K d = 3 × 10-4 mol dm-3 , 25°C, I = 0⋅5 mol dm-3). This complex undergoes (O, O) chelation by the bound bisulphite with k = 1⋅4 × 10-3 s-1 (31°C) to Rh(OH 2) 4 (O 2 SO) + and the chelated sulphito complex takes up another HSO 3 in a fast equilibrium step to yield Rh(OH 2) 3 (O 2 SO)(OSO 2 H) which further undergoes intramolecular ligand isomerisation to the S-bonded sulphito complex: Rh(OH 2) 3 (O 2 SO)(OSO 2)-→ Rh(OH 2) 3 (O 2 SO)(SO 3)-(k iso = 3 × 10-4 s-1 , 31°C). A dinuclear (µ-O, O) sulphite-bridged complex, Na 4 [Rh 2 (µ-OH) 2 (OH) 2 (µ-OS(O)O)(O 2 SO)(SO 3) (OH 2)]5H 2 O with (O, O) chelated and S-bonded sulphites has been isolated and characterized. This complex is sparingly soluble in water and most organic solvents and very stable to acid-catalysed decomposition.

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Section: +supporting

confidence: 87%

Section: +mentioning

confidence: 85%

Section: Rh(oh 2 ) 5 (-Osomentioning

confidence: 99%

Section: +mentioning

confidence: 99%

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Kinetics and mechanism of the reactions of hexaaqua rhodium (III) with sulphur (IV) in aqueous medium

Nayak

Dash

2004

J Chem Sci

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“…30 Our calculated pK a range of 1.7−5.5 is in reasonable agreement with the reported pK a value of Cr(III) around 3.88. 29,73,74 (This calculated pK a has a range due to deprotonation from different coordinated water sites.) The results show that as water is removed from the Cr(III) aqua complex the pK a decreases, thus indicating stronger acidic character of the Cr(III) complex.…”

Section: ■ Experimental Methodsmentioning

confidence: 99%

Mechanistic Study of Enhanced Protonation by Chromium(III) in Electrospray Ionization: A Superacid Bound to a Peptide

Persaud

Dieke

Jing

et al. 2019

J. Am. Soc. Mass Spectrom.

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Addition of trivalent chromium, Cr(III), to solutions undergoing electrospray ionization (ESI) enhances protonation and leads to formation of [M + 2H]2+ for peptides that normally produce [M + H]+. This effect is explored using electronic structure calculations at the density functional theory (DFT) level to predict the energetics of various species that are potentially important to the mechanism. Gas- and solution-phase reaction free energies for glycine and its anion reacting with [Cr(III)(H2O)6]3+ and for dehydration of these species have been predicted, where glycine is used as a simple model for a peptide. For comparison, calculations were also performed with Fe(III), Al(III), Sc(III), Y(III), and La(III). Removal of water from these complexes, as would occur during the ESI desolvation process, results in species that are highly acidic. The calculated pK a of Cr(III) with a single solvation shell is −10.8, making [Cr(III)(H2O)6]3+ a superacid that is more acidic than sulfuric acid (pK a = −8.8). Binding to glycine requires removal of two aqua ligands, which gives [Cr(III)(H2O)4]3+ that has an extremely acidic pK a of −28.8. Removal of additional water further enhances acidity, reaching a pK a of −84.7 for [Cr(III)(H2O)]3+. A mechanism for enhanced protonation is proposed that incorporates computational and experiment results, as well as information on the known chemistry of Cr(III), which is substitutionally inert. The initial step involves binding of [Cr(III)(H2O)4]3+ to the deprotonated C-terminus of a peptide. As the drying process during ESI strips water from the complex, the resulting superacid transfers protons to the bound peptide, eventually leading to formation of [M + 2H]2+.

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Kinetics and mechanism of reaction oftrans-(diaqua)(N,N?-ethylene-bis-salicylidenimine) chromium(iii) with sulfur(iv): The labilizing effect of coordinated sulfite

Dash

Acharya

Mohanty

et al. 1998

Int. J. Chem. Kinet.

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Kinetics and mechanisms of the formation, acid-catalyzed decomposition and intramolecular isomerization of oxygen-bonded (sulfito)pentaaquochromium(III) perchlorate

Cited by 15 publications

References 0 publications

Kinetics and mechanism of the reactions of hexaaqua rhodium (III) with sulphur (IV) in aqueous medium

Kinetics and mechanism of the reactions of hexaaqua rhodium (III) with sulphur (IV) in aqueous medium

Mechanistic Study of Enhanced Protonation by Chromium(III) in Electrospray Ionization: A Superacid Bound to a Peptide

Kinetics and mechanism of reaction oftrans-(diaqua)(N,N?-ethylene-bis-salicylidenimine) chromium(iii) with sulfur(iv): The labilizing effect of coordinated sulfite

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