Original scientific paper

Iron(III) Complexation by Hydroxyurea in Acidie Aqueous Perchlorate Solution

A. Bedrica ; Department of Chemistry, Faculty oj Pharmacy and Biochemistry, University of Zagreb, Zagreb, Croatia, Yugoslavia
M. Biruš ; Department of Chemistry, Faculty oj Pharmacy and Biochemistry, University of Zagreb, Zagreb, Croatia, Yugoslavia
N. Kujundžić ; Department of Chemistry, Faculty oj Pharmacy and Biochemistry, University of Zagreb, Zagreb, Croatia, Yugoslavia
M. Pribanić ; Department of Chemistry, Faculty oj Pharmacy and Biochemistry, University of Zagreb, Zagreb, Croatia, Yugoslavia

Abstract

Equilibrium and kinetic studies were performed to investigate
the complexation of aqueous high spin iron(III) by hydroxyurea
H2NC(O)NH(OH) in acidie solutions at 25 (maintained by NaC104). Complexation has been interpreted in
terms of coordination of the N-O oxygen atom and the NH2
nitrogen atom of the ligand to the iron(III) ion with concomitant
loss of a proton yielding the complex of the molar ratio 1 :1. The
equilibrium quotient for the formation of mono(hydroxyureato)iron
(III) complex is found to be Kl = 1.4. The kinetic results suggest
a parallel path mechanism involving substitution on Fe(H20)63+
and Fe(H20l50H2+ by the hydroxyurea, HU:
Fe (HzO)63+ + HU ;;= Fe (HzO)4 U2++ H+
Fe (H20)s (OH)2++ HU;;=' Fe (HzO)4 U2'
The formation of the complex occurs by the rate constants
kl = 16.8 M-l S-I and k1' = 5450 M" S-I. The analogous rate eonstants
for the reverse hydrolysis reactions were obtained as k-l =
= 11.8 M-l S-I and k_1' = 6.3 S-I. The results are compared with
kinetic data previously reported for the different mono(hydroxamato)
iron(III) complexes.

Keywords

Hrčak ID:

175867

URI

https://hrcak.srce.hr/175867

Publication date:

28.4.1988.

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