Deactivation of the Chlorosulfonate Ion Coordinated to Pentaamminecobalt(III)

Authors: Fairlie D.P.; Dutton B.H.; Mckeon J.A.; Jackson W.G.

Source: Inorganic Reaction Mechanisms, Volume 4, Numbers 3-4, 1 January 2002 , pp. 197-208(12)

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Abstract:

The synthesis and properties of [(NH₃)₅CoOSO₂Cl](ClO₄)₂ are described. This complex is one of the most reactive cobalt(III) species ever isolated (t_1/2 10 s; 25°C; 0.1 M HClO₄). In water it yields [(NH₃)₅CoOSO₃]⁺, [(NH₃)₅CoOH₂]³⁺ and [(NH₃)₅CoCl]²⁺. The first two of these products come from the expected direct S-Cl and Co-O cleavages. The chloro complex arises via intramolecular linkage isomerisation to the transient [(NH₃)₅Co-ClSO₃]²⁺ species which then cleaves the S-Cl bond. Considerable attention is given to the characterisation of the Co-O₃SCl species, including reaction in ¹⁷O-H₂O where the NMR spectra confirm Co-¹⁷OSO₃, Co-¹⁷OH₂ and free ¹⁷OSO₃^2- products. The reactions have been studied also in aqueous base, 0.1 M HClO₄ and Me₂SO where the same reactions are observed but in quite different proportions. In liquid ammonia, with or without added NH₄⁺, no O-bonded sulphamate complex [(NH₃)₅CoOSO₂NH₂]²⁺ arising from direct S-Cl cleavage is observed. The linkage isomerisation pathway is more pronounced in the absence of base, and this is usual. Mechanisms are discussed in relation to the analogous Co(III)-FSO₃^- chemistry and to the hydrolysis reactions of the free FSO₃^- and ClSO₃^- anions. The most remarkable result is that the ClSO₃^- ion (and likely FSO₃^- as well) is substantially deactivated on coordination to Co(III), and such protection is most unusual and no doubt the reason for a successful isolation of the complex of a ligand which hydrolyses in millisec. It can be recovered substantially intact by rapid recrystallisation from water.

Keywords: Cobalt; Synthesis; Chlorosulfonate; Oxygen NMR; Deactivation

Document Type: Research article

DOI: http://dx.doi.org/10.1080/1028662021000062626

Publication date: 2002-01-01

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Deactivation of the Chlorosulfonate Ion Coordinated to Pentaamminecobalt(III)

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