Bis(Trimethylenediamine) Cobait (III) Mediated Hydrolysis of Tripolyphosphate and Trimetaphosphate: Mechanistic Considerations
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Date
1991-07
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Addis Ababa Universty
Abstract
The hydrolysis of tripolyphosphate ( pppi ) and trimetaphosphate
(mpppi ) at 10'3 M concentration by
[tn 2Co(OH)(0H2 )]^, (tn = trimethylenediamine), using
Eu2 f /H+ quenching was investigated. The europium quenching
was adopted since other methods interfere with phosphate
analysis. The reactions were monitored by measurement of
orthophosphate (pi ), pyrophosphate (ppi ), tripolyphosphate
( pppi ) and trimetaphosphate ( mpppi ) in the quenched
aliquots of the reaction mixtures of the reagents. A
method was developed to separate and determine the
different phosphate species in the orthophos phate form
using acetone- phosphomolybdate complex as the analytical
reagent. The reactive species with regard to the
hydrolysis were found to be a 3: 1 tn2Co( 111)ppp i and
tn2Co( 111)mpppi complexes. The results showed larger
amounts of hydrolytic products for the directly added
systems than those of stepwise additions . The production
of phosphites in the reaction solution that contain
[tn2Co(OH )(0H 2)j* and tri metaphosphate was ob served .
Spectrophotometric determination of the phosphite was
done by first oxidising it with iodine to orthophosphate
and using acetone-phospho molybdate complex as the
analytical reagent . Factors affecting the formation and
degradation of the reactive and unreactive species have
been discussed and plausible mechanisns formulated .
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Keywords
Tripolyphosphate and Trimetaphosphate