E/Z isomerization of 3-hydrazonocamphor promoted by coordination to palladium or platinum

3-Hydrazonocamphor, 3-((RRNN)-N-1) C10H14O (R = Me, R-1 = H), undergoes intramolecular hydrogen bridging by coordination to platinum or palladium. This effect is evidenced by considerable decrease in the eta(C = O) frequency (compared to the free ligand) in the IR spectra of the complexes [MCl2L2] (M = Pd, Pt; L = 3-((RRNN)-N-1)C10H14O) as well as by the magnetic non-equivalence of the two ligands, as revealed by C-13 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, R-1 = Me (1), R = Me, R-1 = H (2) and M = Pd; L: R = Me, R-1 = 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 P4(3) space group.