Synthesis and characterization of polyfluorinated 2,2′-bipyridines and their palladium and platinum complexes, [MX2(bis(RfCH2OCH2)-2,2′-bpy)] (X = Cl, Br)

The fluorous-ponytailed bpy ligands at 4,4′ and 5,5′-positions, 4,4′-bis(RfCH2OCH2)-2,2′-bpy and 5,5′-bis(RfCH2OCH2)-2,2′-bpy, were prepared. Then these two differently positioned bpy ligands with varying fluorous lengths were treated with [PdCl2(CH3CN)2], [PtCl2(CH3CN)2], or the simple PtBr2 salt to result in the corresponding 4,4′- or 5,5′-metal halide-containing complexes, [MX2(bis(RfCH2OCH2)-2,2′-bpy)] [M = Pd or Pt; X = Cl or Br]. All of these ligands and metal complexes were fully characterized by multi-nuclei NMR (1H, 19F, and 13C) and FTIR spectroscopy and mass spectrometry (GC/MS, EI and CI, or FAB). Additionally, single crystals of the Pd and Pt complexes with two bpy ligands were successfully obtained, and their X-ray structures are compared with their analogues.

Both 4a and 6a show the two ponytails with the ethereal linkage being more easily rotated, and the two poly-fluorinated ponytails are situated in a way that they are perpendicular to the square plane of the core metal center. In contrast, the structures of complexes 3a and 5a are shown for comparison.Figure optionsDownload as PowerPoint slideHighlights
► Intramolecular five-membered CH…O weak hydrogen bonding.
► Unusual 8-membered cavities formed by CH…FC and CF…HC weak interactions.
► The interconnected dimer with the shorter Pt…Pt distance of 3.504 Å.