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|Title:||Ligand control on the reactions of transition metal complexes with sulphur(IV): Kinetics and mechanism of the reaction of trans-(diaqua) (N,N'-propylene 1,2-bissalicylidiniminato) iron(III) with sulphur(IV) in aqueous medium.|
Dash, Anadi C
|Abstract:||The reaction of trans-[Fe(Salpn 1,2)(OH2)2]+ (Salpn 1,2 = N,N'-propylene 1,2 -bis-salicylidiniminate) with SIV has been studied at 20.0 ≤ t/ oC ≤ 35.0, 0.01 < [SIV]T/mol dm-3 < 0.10 (I= 0.3 mol dm-3) in aqueous acetate buffer medium of varying pH (= 3.80 - 5.20). The stopped flow and rapid scan spectrophotometric measurements indicate the formation of monosulphito complex, trans-[Fe(Salpn 1,2)(OH2)(SO3)]-. The trans-diaqua complex reacts with HSO3-~10 times slower than its (hydroxo aqua) analogue thus displaying the labilising effect of the coordinated hydroxo group. The limiting dissociative mechanism (D) appears to be applicable for the aqua ligand substitution of the aqua-hydroxo complex, trans[Fe(Salpn 1 ,2)(OH2)(OH)]. The trans-[Fe((Salpn 1,2)(OH2)(SO3)]- undergoes redox reaction yielding FeII, SO42- and S2O62-; kobs = k1 rcd + k2 rcd [HSO3-] + k3 rcd [H+][HSO3-] is obeyed with k1 rcd = (0.64 ± 0.40) ×10-4 s-1, k2 rcd = (1.8 ± 0.9) × 10-4 dm-3 mol-1s-1 and k2 rcd = (1.4 ± 0.1) × 102 dm6 mol-2 s-1 at 30.0oC (I= 0.3 mol dm-3)· The electron transfer is innersphere type for the uncatalysed path (k1 rcd) while the exact mechanism for the HSO3- and (H+ + HSO3-) dependent paths remains equivocal.|
|Appears in Collections:||IJC-A Vol.40A(01) [January 2001]|
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