Premium
Cyanide Exchange on Tl(CN) 4 − in Aqueous Solution Studied by 205 Tl and 13 C NMR Spectroscopy
Author(s) -
Bányai István,
Glaser Julius,
Tóth Imre
Publication year - 2001
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/1099-0682(200107)2001:7<1709::aid-ejic1709>3.0.co;2-s
Subject(s) - chemistry , cyanide , heteronuclear molecule , aqueous solution , nuclear magnetic resonance spectroscopy , carbon 13 nmr , inorganic chemistry , stereochemistry
Dynamics of cyanide exchange between Tl( 13 CN) 4 − and 13 CN − was studied by means 205 Tl and 13 C 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) ×10 6 M −1 s −1 and k OH = 5.4(±0.4) ×10 10 M −2 s −1 . It was shown that the exchange between the two cyano species can be studied, not only by 13 C NMR, but also by 205 Tl 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 − and 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.