PROTON NUCLEAR MAGNETIC RESONANCE STUDIES OF SOME NITRILOTRIACETIC ACID N-METHYLIMINODIACETIC ACID AND IMINODIACETIC ACID COMPLEXES OF PLATINUM(2)

Several 1:1 and 1:2 (metal ion:ligand) complexes of nitrilotriacetic acid (NTA), N-methylimmodiacetic acid (MIDA), and iminodiacetic acid (IDA) with platinum(II) have been isolated, and their proton nmr spectra have been studied in D2O solutions as functions of pH and temperature. The spectra exhibit characteristic AB splitting patterns for the ligand acetate protons, indicating that the metal-ligand bonding is nonlabile (long-lived). In the 1:1 complexes MIDA and IDA are tridentate with a chloride ion occupying the remaining site of the square-planar Pt(II). The 195Pt-1H coupling constants provide insight to the conformation of these complexes. The NTA complex appears to be a polymer in which the ligand bridges adjacent Pt(II) ions. The 1:2 NTA and IDA complexes are assigned the trans configuration, with each ligand forming one acetate ring. The 1:2 MIDA complex is not soluble and probably is a polymer. The infrared spectra of the complexes have been measured to characterize their structures further. © 1969, American Chemical Society. All rights reserved.