4th EucheMs chemistry congress

tuesday, 28-Aug 2012
s688
chem. Listy 106, s587–s1425 (2012)
inorganic Chemistry plus Young inorganic chemistry day
inorganic/bioinorganic reaction mechanisms – iii
o - 1 8 5
new inSiGhtS into the PoLyMeriSAtion
MeChAniSMS for PoLyPhoSPhAzene
PreCurSorS
S. PfirrMAnn 1 , v. BLACKStone 1 , M. BendLe 1 ,
h. heLten 1 , i. MAnnerS 1
1 University of Bristol, School of Chemistry, Bristol,
United Kingdom
Polyphosphazenes, [N = PR ] , represent one of the most
2 n
versatile classes of inorganic polymers. The ability to tune the
chemical and physical properties of these materials through the
substituents R has enabled a broad range of promising
applications. [1] Most of the synthetic methods to phosphazene
polymers suffer from poor molecular weight control and the
formation of broad molecular weight distributions. In 1995 the
first example of the living polymerization route to
polyphosphazenes was reported which involved the treatment of
trichloro(N-trimethylsilyl)-phosphoranimine, Cl P = NSiMe , with
3 3
PCl . 5 [2] In contrast to other routes, this method allows the
molecular weight of the polymer to be controlled by altering the
monomer to initiator ratio to give polydichloro-phosphazenes in
high yield with relatively narrow molecular weight distributions.
Although the discovery of this living polymerization of Cl P = 3
NSiMe has permitted a range of synthetic advances, its
3
mechanism has not been fully elucidated.
Based on recent results using model chemistry [3] we have
now further investigated the mechanism of the PCl -initiated
5
living polymerization of Cl P = NSiMe . These studies give
3 3
interesting results and have shown that the polymerization process
is much more complex than originally proposed.
Furthermore, the phosphite-initiated polymerization
of bromophosphoranimine BrMePhP = NSiMe [4] has been
3
investigated in more detail. It was found that alternative
compounds to phosphites can act as much more active initiators.
references:
1. Allcock, H. R. Chemistry and applications of
polyphosphazenes; Wiley-Interscience: Hoboken, N.J,
2003.
2. Honeyman, C. H.; Manners, I.; Morrissey, C. T.; Allcock,
H. R. J. Am. Chem. Soc. 1995, 117, 7035.
3. Blackstone, V.; Lough, A. J.; Murray, M.; Manners, I.
J. Am. Chem. Soc. 2009, 131, 3658.
4. Huynh, K.; Lough, A. J.; Manners, I. J. Am. Chem. Soc.
2006, 128, 14002.
Keywords: polyphosphazenes; mechanisms; polymerizations;
main group chemistry;
inorganic/bioinorganic reaction mechanisms – iii
o - 1 8 6
redox reACtionS of the
PeroxoMonoSuLfAte ion in the
ferroin/ferriin SySteM
i. fABiAn 1 , G. BeLLer 1 , G. Lente 1
4 th EucheMs chemistry congress
1 University of Debrecen, Department of Inorganic and
Analytical Chemistry, Debrecen, Hungary
- Peroxomonosulfate ion (oxone, HSO ) is a strong, two-
5
electron oxidant also used as an inexpensive and environmentally
friendly agent in advanced oxidation procedures. Experiments
involving oxone add valuable information to the study of reactive
intermediates, may confirm mechanistic considerations regarding
the autoxidation of various substrates and may explore important
aspects of industrial applications.
This presentation reports a kinetic study on the reactions of
oxone in the ferroin/ferriin system (the tris-1,10-phenanthroline
complexes of FeII and FeIII ), which is frequently used for
modelling the redox activity of biological compounds. A complex
kinetic behavior was observed: the concentration of ferroin
decreases in the first stage of the reaction; however, after reaching
a minimum the concentration increases to a maximum and then
decreases again. A similar behavior was described previously in
the reaction of ferroin with Ce(IV). [1]
Detailed kinetic study and ESI mass spectrometry confirmed
the formation of an 1:1 adduct between the reactants in the initial
- phase of the ferroin-HSO reaction. [2] The oxidation product,
5
1,10-phenanthroline-mono-N-oxide was identified in the reaction
mixture with several methods (UV-Vis, ESI-MS, 1H-NMR). The
N-oxide has significant inhibiting effect: upon the addition of the
N-oxide to the initial mixture, a slower consumption of ferroin
was observed. A kinetic model was proposed for the reaction and
independent measurements were carried out with ferriin which is
also formed in the reaction.
Ferriin decomposes in strongly acidic solutions
producing ferroin and 1,10-phenanthroline-mono-N-oxide. 1,10-
Phenanthroline-mono-N-oxide has a slight autocatalytic effect on
the decomposition and increases the rate of ferroin formation. We
4+ propose the formation of Fe(phen) as a minor intermediate in
3
the overall process. [3]
references:
1. M. Melichercik; J. Treindl; J. Phys. Chem. 1989, 93, 7652.
2. G. Bellér; G. Lente; I. Fábián; Inorg. Chem. 2010, 49,
3968.
3. G. Bellér; G. Bátki; G. Lente; I. Fábián; J. Coord. Chem.
2010. 63, 2586.
Keywords: oxone; redox chemistry; reactive intermediate;
AOP; reaction mechanism;
AUGUst 26–30, 2012, PrAGUE, cZEcH rEPUbLIc