Collect. Czech. Chem. Commun. 2007, 72, 649-665

E/Z Isomerization of 3-Hydrazonocamphor Promoted by Coordination to Palladium or Platinum

M. Fernanda N. N. Carvalho*, Ana S. D. Ferreira, João L. Ferreira da Silva and Luís F. Veiros

Centro de Química Estrutural, Complexo I, Instituto Superior Técnico, Universidade Técnica de Lisboa, Av. Rovisco Pais, 1049-001 Lisboa, Portugal


3-Hydrazonocamphor, 3-(RR1NN)C10H14O (R = Me, R1 = H), undergoes intramolecular hydrogen bridging by coordination to platinum or palladium. This effect is evidenced by considerable decrease in the ν(C=O) frequency (compared to the free ligand) in the IR spectra of the complexes [MCl2L2] (M = Pd, Pt; L = 3-(RR1NN)C10H14O) as well as by the magnetic non- equivalence of the two ligands, as revealed by 13C NMR. DFT calculations indicate that coordination of 3-(Me(H)NN)C10H14O promotes E/Z isomerization of the hydrazono group of the ligand, inducing formation of intramolecular hydrogen bonding and corresponding stabilization of the complex. Characterization of the complexes [MCl2L2] (M = Pt; L: R, R1 = Me (1), R = Me, R1 = H (2) and M = Pd; L: R = Me, R1 = H (3)) was performed by analytical and spectroscopic techniques. Redox properties of the 3-hydazonocamphors and their complexes were studied by cyclic voltammetry. The structure of trans-[PtCl2{3-(Me2NN)C10H14O}2] was determined by single-crystal X-ray diffraction analysis. The complex has square-planar geometry and crystallizes in the tetragonal P43 space group.

Keywords: Platinum complexes; Palladium; Camphorimine; Hydrazones; Hydrogen bonding; DFT calculations; Cyclic voltammetry; IR spectroscopy.

References: 42 live references.