Unprecedented Formation of a Formally Cu(III) Trifluoromethyl Hydroxide Tetramer

Aerobic copper-mediated oxidative processes play a pivotal role in the context of enzymatic oxidation and catalysis. Herein, the first high-valent copper(III) trifluoromethyl hydroxide with the tetrameric heterocubane structure [Cu(CF3)2(OH)]4 was synthesized by air oxidation of copper(I) in the presence of TMSCF3/KF and fully characterized, including X-ray crystallography. This unique compound displays versatile reactivity, functioning as a hydroxide base in neutralization reactions with acids, which affords a broad variety of high-valent Cu(III) complexes with two trifluoromethyl groups. The synthetic relevance of copper(III) trifluoromethyl hydroxide for boronic acid trifluoromethylation was demonstrated. The natural population analysis (NPA) charge distribution in the tetrameric heterocubane was studied by DFT calculations, which support the experimentally observed behavior of this compound as a weak hydroxide base, and revealed the positive NPA charge of +1.157 on high-valent copper.