Multifaceted Lewis Acidity of a High-Valent Cu(III) complex

Copper(III) compounds are of crucial importance in biological systems and aerobic oxidative processes, whereas their Lewis acidity, a key reactivity feature, is barely studied. Herein we report the multifaceted reactivity of the copper(III) hydroxide tetramer [Cu(OH)(CF3)2]4 with amide or phosphine oxide Lewis bases to give dimeric adducts with different types of metal-ligand coordination. Addition of weak Lewis bases (solvents) leads to the formation of adducts with µ2-coordination of the ligand, where the tetrameric heterocubane scaffold is preserved. The Lewis acidity of the tetrameric hydroxide was evaluated using DFT calculations and Gutmann-Beckett analysis and compared to the elusive and hypothetical inorganic and organometallic copper(III) species. Accordingly, the Lewis acid strength increases in the order PyCu(CF3)3 < [Cu(CF3)2(OH)]4 < Cu(CF3)2OH < Cu(CF3)3 ~ CuF3 < Cu(C6F5)3 < Cu(OTeF5)3