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.