Reactions of µ-hydroxo-dicobalt(III) complexes. Part X. Kinetic studies of the reaction of the µ-amido-µ-hydroxo-bis[tetra-amminecobalt(III)] complex with phosphate ions in aqueous perchloric acid solutions and the characterisation of the µ-amido-µ-phosphato-bis[tetra-amminecobalt(III)] complex

Abstract

base hydrolysis reactions 3?4 of these complexes have also been studied and it has been possible to identify rate constants for the aquation of mono-, di-, and triprotonated phosphato-species. $ In this paper details are presented of the preparation of the p-amido-pphosphato-bis[tetra-amminecobaIt(~~~)]complex in its monoprotonated and unprotonated forms (as the nitrate and bromide salts respectively) and the identification of a diprotonated form in acidic solution. 1.r. and u.v.visible spectra and molecular formulae, as determined by elemental analyses, support p-phosphato-structures. The complexes are analogous to the p-amido-p-sulphatoand p-amido-p-selenato-complexes reported previously.

Silicic Acid Adsorption and Oligomerization at the Ferrihydrite−Water Interface: Interpretation of ATR-IR Spectra Based on a Model Surface Structure

“…The acidity of protons on oxyacids that are coordinated to metal cations can be assessed from the p K A ’s of solution complexes such as [(NH 3 ) 4 Co·μ(NH 2 ,H 2 PO 4 )·Co(NH 3 ) 4 ] 4+ , which has an H 2 PO 4 − group bridging two Co 3+ cations. The p K A ’s of this complex (1.5 and 6.0) were close to the p K A1 and p K A2 of H 3 PO 4 , indicating that the effect of two Co 3+ ions on the acidity of the remaining OH groups was approximately equivalent to one H + . This is consistent with the nonprotonated bidentate PO 4 3− ligand on goethite being protonated between pH 8.4 and 4.5 (p K A2 H 3 PO 4 = 7.2).…”

“…The pK A 's of this complex (1.5 and 6.0) were close to the pK A1 and pK A2 of H 3 PO 4 , indicating that the effect of two Co 3þ ions on the acidity of the remaining OH groups was approximately equivalent to one H þ . 37 This is consistent with the nonprotonated bidentate PO 4 3ligand on goethite being protonated between pH 8.4 and 4.5 (pK A2 H 3 PO 4 = 7.2). Therefore, it is reasonable that the (tFe) 2 O 2 Si(OH) 2 complex on the ferrihydrite surface would be less acidic than H 4 SiO 4 in solution as indicated by the IR spectra in this work.…”

Mechanistic Studies on the Reactions of Molybdenum(VI), Tungsten(VI), Vanadium(V), and Arsenic(V) Tetraoxo Anions with the FeIIFeIII Form of Purple Acid Phosphatase from Porcine Uteri (Uteroferrin)

“…The reaction which models most closely the formation of a μ-phosphato product is that involving the interconversion of [NH 3 ] 4 Coμ(NH 2 ,OH)Co(NH 3 ) 4 ] 4+ and [(NH 3 ) 4 Coμ(NH 2 , H 2 PO 4 )Co(NH 3 ) 4 ] 4+ in the presence of H + /[H 2 PO 4 ] - , as indicated in (11) . Similar reactions of other tetraoxo and related anions have been reported .…”

Reactivity of Phosphate Diesters Doubly Coordinated to a Dinuclear Cobalt(III) Complex: Dependence of the Reactivity on the Basicity of the Leaving Group

“…The amounts of charge on the phenolic oxygen in phenolate anion, in singly protonated phenyl phosphate, and in doubly protonated phenyl phosphate are −1, 0.74, and 0.83, respectively . If we assume that the amount of charge in the phenolic oxygen of 1d is about the same as that in doubly protonated phenyl phosphate, the total change in the charge upon hydrolysis of 1d is expected to be −1 − 0.83 = −1.83. Since the value of β lg is −1.38 for the hydrolysis of 1a to 1d , the extent of P−O bond cleavage at the transition state for the reactions is estimated to be about −1.38/−1.83 = 0.77.…”