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.
Jancsó
A
A
Department of Inorganic and Analytical Chemistry, University of Szeged, Hungary.
Gajda
T
T
Szorcsik
A
A
Kiss
T
T
Henry
B
B
Vankó
G
G
Rubini
P
P
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