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.

Graphical abstractBoth 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 full-size imageDownload 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.