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 ^<i>t</i>BuNC 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