O 2 Activation at a Low-Valent P-Center: Isolation of a Cyclic Alkyl(Amino) Carbene (cAAC)-Phosphonate-Supported Dicationic Cu(II) 6 Cluster

Herein, we explore the coordination behavior and O 2 -activation of molecular diphosphorus (P 2 ) in the presence of CuX (X = Cl, Br), unraveling the phosphinidene nature of low-valent phosphorus atoms. Both mono- and dicuprated P 2 complexes with general formula [(cAAC) 2 P 2 (CuX) n ] (cAAC = cyclic alkyl(amino) carbene, n = 1, X = Cl ( 2a – 2b ), Br ( 2c ); n = 2, X = Cl ( 3a – 3b ), Br ( 3c )) are isolated in the solid state. Aerial oxidation of bis-cAAC-supported P 2 in the presence of Cu(I) ions afforded the paramagnetic dicationic Cu(II) 6 cluster [Cu 6 II (Cy-cAAC-PO 3 ) 4 O 2 Cl 2 ][CuCl 2 ] 2 ( 4 ), stabilized by cAAC-phosphonate ligands with μ 3 -P atoms. EPR studies revealed the in situ generation of a P-centered monoradical intermediate upon exposure of the monocuprated P 2 to atmospheric oxygen, followed by oxidation of Cu(I) to Cu(II). All complexes are structurally characterized by single-crystal X-ray diffraction. Quantum chemical calculations are performed to explore the nature of chemical bonding and the electron density distribution of 2 and 3 . Mulliken spin density calculations revealed the open-shell nature of cluster 4, featuring the Cu(II) ions, which was further supported by XPS, EPR, and magnetic measurements.