Three-Coordinate Copper(II) Aryls: Key Intermediates in C–O Bond Formation

Copper­(II) aryl species are proposed key intermediates in Cu-catalyzed cross-coupling reactions. Novel three-coordinate copper­(II) aryls [CuII]-C6F5 supported by ancillary β-diketiminate ligands form in reactions between copper­(II) alkoxides [CuII]-OtBu and B­(C6F5)3. Crystallographic, spectroscopic, and DFT studies reveal geometric and electronic structures of these Cu­(II) organometallic complexes. Reaction of [CuII]-C6F5 with the free radical NO(g) results in C-N bond formation to give [Cu]­(η2-ONC6F5). Remarkably, addition of the phenolate anion PhO– to [CuII]-C6F5 directly affords diaryl ether PhO-C6F5 with concomitant generation of the copper­(I) species [CuI]­(solvent) and {[CuI]-C6F5}−. Experimental and computational analysis supports redox disproportionation between [CuII]-C6F5 and {[CuII]­(C6F5)­(OPh)}− to give {[CuI]-C6F5}− and [CuIII]­(C6F5)­(OPh) unstable toward reductive elimination to [CuI]­(solvent) and PhO-C6F5.