Design, synthesis, and evaluation of unsymmetrical difluoro-boron complexes with imidazoline as potential fungicides

A series of unsymmetrical difluoroboron (BF₂) complexes with pyridine and imidazoline were synthesized by reaction of new chelating ligands (arylmethyl-imidazolidinylidene)-pyridin-2-yl-amine with boron trifluoride diethyl etherate. All the ligands and BF₂ complexes were structurally characterized by IR, HRMS, ¹H, ¹³C, ¹¹B, and ¹⁹F NMR,indicating the bidentate complexation of imidazoline nitrogen and the pyridine nitrogen to the boron center. Evaluation of agricultural bioactivities showed that some of the BF2 complexes exhibited moderate fungicidal activities, and most of the BF₂ complexes exhibited higher activities than the none-BF₂ complexed substrates.