PROTON MAGNETIC RESONANCE STUDIES OF AMINO ACID COMPLEXES OF PLATINUM(2) .I. SYNTHESIS SPECTRAL INTERPRETATION AND CONFORMATIONAL IMPLICATIONS

Proton nmr spectra of Pt(II) complexes of six different types of amino acids (1-6) have been analyzed. The effects of coordination and of proton titration on chemical shifts of skeletal protons and the presence or absence of 195Pt side bands have been used to determine the coordination sites in multidentate ligands. Several different types of isomerism, including that resulting from creation of a new asymmetric center by coordination to the metal atom, are revealed by the spectra. A strong conformation dependence for 195Pt-1H spin coupling constants, which vary from about 10 to 60 Hz in Pt-N-C-H fragments, is suggested by the data. Simultaneous determination of Jpt-H and JH-H in several of the complexes indicates that Jpt-H for Pt-N-C-H fragments is a maximum for dihedral angles (φ) near 180° and approaches a minimum for φ = 0°. This conclusion is used to determine preferred conformations of other coordinated ligands. © 1968, American Chemical Society. All rights reserved.