Fluorinated B-phenylated scorpionates as tunable platforms for stabilizing thallium(i) and silver(i)–ethylene complexes

Abstract

Fluorinated and B-phenylated bis(pyrazolyl)borate and bis(pyridyl)borate ligands have been utilized in thallium(I) and silver(I)–ethylene chemistry. These ligands contain electron-withdrawing trifluoromethyl or pentafluorosulfanyl groups that create a chemically inert half-rim and, together with a flanking phenyl group, provide steric protection at the metal site. Thallium(I) complexes display κ²-N,N ligand binding and noteworthy Tl–F coupling in ¹⁹F NMR, indicating proximity effects of the fluorinated substituents. The silver–ethylene complexes [Ph₂B(3-(CF₃)Pz)₂]Ag(C₂H₄), [Ph₂B(3-(SF₅)Pz)₂]Ag(C₂H₄), and [Ph₂B(6-(CF₃)Py)₂]Ag(C₂H₄) feature trigonal-planar silver(I) sites, with NMR data showing upfield shifts for ethylene proton and carbon resonances relative to those of the free ethylene. The steric effects of fluorinated supporting ligands in thallium and silver complexes were evaluated using buried-volume calculations. In addition, C–H activation of alkanes via carbene insertion catalyzed by silver complexes is reported. Overall, the findings illustrate how fluorinated groups and N-heterocyclic donor arms influence metal–ligand bonding, the stability of coinage-metal π-complexes, and influence the catalytic efficiency and selectivity in alkane C–H functionalization.