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Salts of one series of [Co en2L Cl]2+ cations have been prepared, where en represents bidenate ethylenediamine and L is a diamine acting as a unidentate ligand. They are tentatively assigned a cis-configuration on the basis of their visible spectra. The base strength of the diamines are decreased by factors of 103–107 when the other {NH2} end is coordinated to cobalt(III), and in 0·1 mol dm−3 acid, the complexes exist as the corresponding protonated forms [Co en2(LH)Cl]3+. The rate constants for both spontaneous and mercury(II)-induced aquations of these trivalent cations have been determined over a range of temperatures and the activation parameters calculated. The results are compared with data obtained for the divalent cis-chloro-n-butylaminebis(ethylendiamine)cobalt(III) cation with a view to investigate the effect of substrate charge on reactivities.
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