Abstract
The synthesis and properties of [(NH 3 ) 5 CoOSO 2 Cl](ClO 4 ) 2 are described. This complex is one of the most reactive cobalt(III) species ever isolated ( t 1/2 10 s; 25C; 0.1 M HClO 4 ). In water it yields [(NH 3 ) 5 CoOSO 3 ] + , [(NH 3 ) 5 CoOH 2 ] 3+ and [(NH 3 ) 5 CoCl] 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 [(NH 3 ) 5 Co-ClSO 3 ] 2+ species which then cleaves the S-Cl bond. Considerable attention is given to the characterisation of the Co-O 3 SCl species, including reaction in 17 O-H 2 O where the NMR spectra confirm Co- 17 OSO 3 , Co- 17 OH 2 and free 17 OSO 3 2 products. The reactions have been studied also in aqueous base, 0.1 M HClO 4 and Me 2 SO where the same reactions are observed but in quite different proportions. In liquid ammonia, with or without added NH 4 + , no O-bonded sulphamate complex [(NH 3 ) 5 CoOSO 2 NH 2 ] 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)-FSO 3 chemistry and to the hydrolysis reactions of the free FSO 3 and ClSO 3 anions. The most remarkable result is that the ClSO 3 ion (and likely FSO 3 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.