Synthesis, Characterization, and Unique Catalytic Activities of a Fluorinated Nickel Enolate

We have synthesized a new nickel enolate [(PhCOCF2)Ni(dcpe)][FB(C6F5)(3)] featuring fluorine atoms on the enolate moiety via B(C6F5)(3)-promoted C-F bond activation of alpha,alpha,alpha-trifluoroacetophenone. X-ray diffraction study of [(PhCOCF2)Ni(dcpe)][FB(C6F5)(3)] revealed that the complex had adopted an eta(3)-oxallyl coordination mode in the crystal lattice. The reaction of (BuNC)-Bu-t with [(PhCOCF2)Ni(dcpe)][FB(C6F5)(3)] resulted in the coordination of isocyanide to the nickel center to form a C-bound enolate complex. The reactions of [(PhCOCF2)Ni(dcpe)][FB(C6F5)(3)] with aldehydes gave insertion products quantitatively which were fully characterized by NMR spectroscopy. Furthermore, we established unique catalytic applications for [(PhCOCF2)Ni(dcpe)][FB(C6F5)(3)] toward a Tishchenko reaction, along with a highly selective crossed-esterification of alpha,alpha,alpha-trifluoroacetophenones with aldehydes.