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 α,α,α-trifluoroacetophenone. X-ray diffraction study of [(PhCOCF2)­Ni­(dcpe)]­[FB­(C6F5)3] revealed that the complex had adopted an η3-oxallyl coordination mode in the crystal lattice. The reaction of tBuNC 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 α,α,α-trifluoroacetophenones with aldehydes.