Binuclear copper(I) macrocycles synthesized via the weak-link approach

The weak-link approach has been employed to synthesize a series of bimetallic Cu(I) macrocycles in high yield. Addition of phosphinoalkylether or -thioether ligands to [Cu(MeCN)₄]PF₆ produces "condensed" intermediates, [μ-(1,4-(PPh₂CH ₂CH₂X)₂Y₂)Cu₂][PF ₆]₂ (X = S, O; Y = C₆H₄, C ₆F₄), containing strong P-Cu bonds and weaker O-Cu or S-Cu bonds. The weak bonds of these intermediates can be cleaved through ligand substitution reactions to generate macrocyclic structures, [μ-(1,4-(PPh ₂CH₂CH₂X)₂Y)₂(Z) _nCu₂][PF₆]₂ (X = S, O; Y = C ₆H₄, C₆F₄; Z = pyridine, acetonitrile, diimines, isocyanide) in nearly quantitative yields. The incorporation of tetrahedral Cu(I) metal centers into these macrocycles provides a pathway to complexes that differ from analogous d⁸ square planar macrocycles generated via this approach in their increased air stability, small molecule reactivity, and ability to form multiple structural isomers. Solid-state structures, as determined by single-crystal X-ray diffraction studies, are presented for condensed intermediates and an open macrocycle.