التفاصيل البيبلوغرافية
| العنوان: |
Di-oxo and tri-oxo Re(VII)-oxosulfato complexes in the Re2O7-K2S2O7 molten system. Molecular structure, vibrational properties and temperature-dependent interconversion. |
| المؤلفون: |
Andriopoulou, Chrysanthi1,2, Anastasiou, Ioannis1, Boghosian, Soghomon1,2 bogosian@chemeng.upatras.gr |
| المصدر: |
Vibrational Spectroscopy. Jan2019, Vol. 100, p14-21. 8p. |
| مصطلحات موضوعية: |
*LIQUID alloys, *MOLECULAR structure, *METAL complexes, *VIBRATIONAL spectra, *TEMPERATURE measurements, *STATIC equilibrium (Physics) |
| مستخلص: |
Abstract The reaction between Re 2 O 7 and K 2 S 2 O 7 in the molten phase is studied by Raman spectroscopy under static equilibrium oxidative conditions at temperatures of 260–470 °C and in the full composition range, X R e 2 O 7 0 = 0 − 1. Raman band intensity correlations are adequate for inferring a 1:1 stoichiometry for the complex formation reaction. Depending on temperature and on composition of the mixture, two isomeric ReVII-oxosulfato complexes are formed: (a) ReO 3 SO 4 −, prevalent at low temperature (T<300 °C), where penta-coordinated ReVII takes on a tri-oxo termination configuration; and (b) (ReO 2) 2 O 2 (SO 4) 2 2-, dominant at high temperature (T>360 °C), with hexa-coordinated ReVII in di-oxo termination configuration. The characteristic symmetric and antisymmetric stretching modes (ν s / ν a s) of the Re(=O) 3 + and Re(=O) 2 3+ cores are found at 975/938 cm-1 and 989/944 cm-1 for the tri-oxo and di-oxo sites, respectively. A fully reversible temperature-dependent 2ReO 3 SO 4 −(l) ↔ (ReO 2) 2 O 2 (SO 4) 2 2-(l) interconversion equilibrium is evidenced. Consistent molecular structural models are proposed for the ReO 3 SO 4 − and (ReO 2) 2 O 2 (SO 4) 2 2- complexes as well as for their associated/polymeric counterparts, (ReO 3 SO 4) n n- and ((ReO 2) 2 O 2 (SO 4) 2) n 2n-. Molten Re 2 O 7 reacts with K 2 SO 4 according to Re 2 O 7 (l) + 2SO 4 2- → ReO 4 −(l) + S 2 O 7 2-(l). The ReVII-oxosulfato complexes and their configurational, structural and vibrational properties are of interest as references for inferring corresponding properties for dispersed amorphous oxo-ReVII species in supported rhenia catalysts. [ABSTRACT FROM AUTHOR] |
| قاعدة البيانات: |
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