Cyanide exchange on Tl(CN)(4)(-) in aqueous solution studied by Tl-205 and C-13 NMR spectroscopy
2001 (English)In: European Journal of Inorganic Chemistry, ISSN 1434-1948, E-ISSN 1099-0682, no 7, 1709-1717 p.Article in journal (Refereed) Published
Dynamics of cyanide exchange between Tl((CN)-C-13)(4)(-) and (CN-)-C-13 was studied by means Tl-205 and C-13 NMR. The rate law consists of two parts: w = k(CN)[Tl(CN)(4)(-)][CN-] + k(OH)[Tl(CN)(4)(-)][CN-][OH-] with k(CN) = 9.7(+/-0.4) x 10(6) M(-1)s(-1) and k(OH) = 5.4(+/-0.4) x 10(10) M(-2)s(-1). It was shown that the exchange between the two cyano species can be studied, not only by C-13 NMR, but also by Tl-205 NMR using the heteronuclear carbon-thallium scalar coupling as an indicator, despite the fact that only one Tl site is present in the system. The reaction mechanism is discussed in terms of an associative interchange mechanism, I-A. Penetration of the incoming cyanide ion into the coordination sphere of Tl(CN)(4)(-) Tl(CN)(4)(OH)(-) is suggested to be the rate-determining step for the two parallel reactions paths. Possible reasons for the strong labilizing effect of the cyanide ligand is discussed in the light of thermodynamic and structural data. The possibility of detection of an exceptional exchange reaction, namely cyanide exchange between two Tl(CN)(4)(-) entities by a direct encounter was theoretically settled, but found to be too slow to be detected.
Place, publisher, year, edition, pages
2001. no 7, 1709-1717 p.
ligand exchange, thallium, cyanides, TlNMR, nuclear magnetic-resonance, equilibrium dynamics, chemical exchange, hydrogen-cyanide, spy nuclei, complexes, system, relaxation, kinetics, bromide
IdentifiersURN: urn:nbn:se:kth:diva-20775ISI: 000169787900009OAI: oai:DiVA.org:kth-20775DiVA: diva2:339472
QC 201005252010-08-102010-08-10Bibliographically approved