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 [Cu]-CF supported by ancillary β-diketiminate ligands form in reactions between copper(II) alkoxides [Cu]-OBu and B(CF). Crystallographic, spectroscopic, and DFT studies reveal geometric and electronic structures of these Cu(II) organometallic complexes. Reaction of [Cu]-CF with the free radical NO results in C-N bond formation to give [Cu](η-ONCF). Remarkably, addition of the phenolate anion PhO to [Cu]-CF directly affords diaryl ether PhO-CF with concomitant generation of the copper(I) species [Cu](solvent) and {[Cu]-CF}. Experimental and computational analysis supports redox disproportionation between [Cu]-CF and {[Cu](CF)(OPh)} to give {[Cu]-CF} and [Cu](CF)(OPh) unstable toward reductive elimination to [Cu](solvent) and PhO-CF.