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Thermodynamic and spectroscopic study of the binding of dimethyltin(IV) by citrate at 25 °C
Author(s) -
Cardiano Paola,
Giuffrè Ottavia,
Pellerito Lorenzo,
Pettignano Alberto,
Sammartano Silvio,
Scopelliti Michelangelo
Publication year - 2006
Publication title -
applied organometallic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.53
H-Index - 71
eISSN - 1099-0739
pISSN - 0268-2605
DOI - 10.1002/aoc.1076
Subject(s) - chemistry , chemical stability , aqueous solution , ligand (biochemistry) , potentiometric titration , octahedron , metal , stability constants of complexes , mössbauer spectroscopy , crystallography , stereochemistry , inorganic chemistry , crystal structure , organic chemistry , biochemistry , receptor , electrode
Thermodynamic (potentiometric and calorimetric) and spectroscopic ( 1 H NMR, 119 Sn Mössbauer) studies were performed in aqueous solution in order to characterize the interaction of dimethyltin(IV) cation with citrate ligand. Six species {(CH 3 ) 2 Sn(cit) − ; [(CH 3 ) 2 Sn] 2 (cit) 2 2− ; (CH 3 ) 2 Sn(cit)H 0 ; (CH 3 ) 2 Sn(cit)OH 2− ; [(CH 3 ) 2 Sn] 2 (cit)OH 0 ; [(CH 3 ) 2 Sn] 2 (cit)(OH) 2 − } were found. All the species formed in this system are quite stable and formation percentages are fairly high. For example, at pH = 7.5 and C (CH 3 ) 2 Sn= C cit = 10 mmol l −1 , Σ% for [(CH 3 ) 2 Sn] 2 (cit)(OH) 2 − and (CH 3 ) 2 Sn(cit)OH 2− species reaches 65%. Overall thermodynamic parameters obtained show that the main contribution to stability is entropic in nature. Thermodynamic parameters were discussed in comparison with a simple tricarboxylate ligand (1,2,3‐propanetricarboxylate). Two empirical relationships were derived from thermodynamic formation parameters. Spectroscopic results fully confirm the speciation model defined potentiometrically and show the mononuclear species to have an eq‐(CH 3 ) 2 Tbp structure with different arrangements around the metal, while for [(CH 3 ) 2 Sn] 2 (cit)(OH) 2 − there are two different Sn(IV) environments, namely trans ‐(CH 3 ) 2 octahedral and cis ‐(CH 3 ) 2 Tbp. Copyright © 2005 John Wiley & Sons, Ltd.