Potentiometric and spectroscopic studies on the dimethyltin(IV) complexes of 2-hydroxyhippuric acid.
Equilibrium and spectroscopic (1H, 13C NMR and 119Sn Mössbauer) studies in aqueous solution are reported for dimethyltin(IV) complexes of 2-hydroxyhippuric acid (Sal-Gly). Below pH 4, oxygen-coordinated complexes MLH and ML are formed. In the pH range 5-8.5, the species MLH(-1), predominates at any metal-to-ligand ratio. The ligand exchange of this species is slow on the NMR time scale, which allows its structural characterization by NMR spectroscopy: the coordination polyhedron around the tin atom is distorted trigonal bipyramidal, with tridentate [O-,N-,COO-] coordination of Sal-Gly, involving two equatorial methyl groups. The NMR results reveal that the main cause of the distortion of the polyhedron is the large CH3-Sn-CH3 angle of 136+/-4 degrees. The presented results supplement the data available on the dimethyltin(IV)-promoted amide deprotonation of peptides, and provide further arguments for the fundamental role of the carboxylate as an anchoring group in this process.
Department of Inorganic and Analytical Chemistry, University of Szeged, Hungary.
A
A
Jancsó
T
T
Gajda
A
A
Szorcsik
T
T
Kiss
B
B
Henry
G
G
Vankó
P
P
Rubini
D004563:Electrochemistry; D006626:Hippurates / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D009682:Magnetic Resonance Spectroscopy; D015394:Molecular Structure; D009947:Organotin Compounds / Q000737:chemistry*; D012996:Solutions / Q000737:chemistry; D015204:Spectroscopy, Mossbauer
D006626:Hippurates; D009947:Organotin Compounds; D012996:Solutions; C030514:hippuric acid