Oxygenation of [Tris(2-pyridyl)amine](trifluoromethanesulfonato)copper(I) in Nonaqueous Solvents. Synthesis and Structural Characterization of the Cubane-like Cluster [Cu₄(OH)₄(SO₃CF₃)₂[N(C₅H₄N)₃]₄][SO₃CF₃]₂·C₃H₆O

A product of the reaction of molecular oxygen with [tris(2-pyridyl)amine](trifluoromethanesulfonato)copper(I) has been characterized by a low-temperature X-ray diffraction analysis and found to be a cubane-like tetramer of formula [Cu₄-(OH)₄(SO₃CF₃)₂[N(C₅H₄N)₃]₄][SO₃CF₃]2·C₃H₆O, with cupric ions and hydroxyl oxygen atoms at alternating vertices of a cube. Each cupric ion is essentially octahedrally coordinated, being bound to three OH bridges, two pyridine N atoms, and one triflate O atom. The cube is of approximate D_2d symmetry, the elongation along one axis possibly arising as a consequence of Jahn-Teller distortion. In this complex the tris(2-pyridyl)amine acts as a bidentate rather than a tridentate ligand and each triflate ligand spans two vertices of the cluster. Magnetic susceptibility measurements reveal that the cupric ions in the cube are antiferromagnetically coupled, and this observation is readily rationalized on the basis of the structural data. Isotopic tracer experiments demonstrate that the hydroxyl oxygen atoms in the product originate largely in the molecular oxygen used in the reaction and that the hydrogen atoms originate largely in other tris(pyridyl)amine molecules. The material crystallizes with four formula units in space group C⁵_2h-P2₁/n of the monoclinic system in a cell of dimensions a = 18.848 (7) Å, b = 13.804 (5) Å, c = 29.491 (10) Å, and β = 99.29 (3)°. The structure has been refined isotropically to an R index of 0.098 on the basis of 337 variable parameters and 8904 unique observations obtained at −150 °C.