Synthesis and solution behavior of the trinuclear palladium(II) unsaturated carboxylate complexes triangle-Pd3[μ-O2CC(R′) = CHMe]6 (R′ = Me, H): X-ray structure of palladium(II) tiglate (R′ = Me)

The first examples of binary palladium(II) derivatives of unsaturated carboxylic acids are reported. It was found that the interaction of Pd3(μ-OAc)6 with the α,β-unsaturated 1-methylcrotonic (tiglic) and crotonic acids leads to the corresponding carboxylates of composition Pd3[μ-O2CC(R′) = CHMe]6, where R′ = Me (1) or H (2). The new compounds have been characterized by elemental analysis, solid and solution IR, 1H and 13C NMR, and ESI mass spectrometry. The crystal structure of 1 has been determined. This molecule displays a central Pd3 cyclic core with Pd–Pd distances of 3.093–3.171 Å. Each Pd–Pd bond is bridged by a pair of carboxylate ligands, one above and the other below the Pd3 plane, providing a square planar coordination for each Pd atom in an approximate D3h overall symmetry arrangement. Solution spectroscopic data show that the bridging η1:η1:μ2 interaction of the carboxylates of 1 and 2 is readily displaced, with a change of the ligand to the terminal (η1) coordination mode.

Graphical abstractThe first examples of binary palladium(II) derivatives of unsaturated carboxylic acids have been prepared by reaction of palladium acetate with the α,β-unsaturated carboxylic acids 1-methylcrotonic (tiglic) and crotonic acids.Figure optionsDownload full-size imageDownload as PowerPoint slide