Copper(i) halide clusters based upon ferrocenylchalcogenoether ligands: Donors, halides and semi-rigidity effects on the geometry and catalytic activity

Six copper(i) halide clusters based upon ferrocenyltelluroethers or ferrocenylselenoethers, 1-6, have been synthesized and structurally characterized by an X-ray crystallographic study. These structures include a discrete step-cubane Cu₄I₄ cluster, a 1D chain with rhomboid Cu₂X₂ clusters, a 1D chain with cubane Cu₄I₄ clusters and a 2D network with Cu₂I₂ clusters. 1-3 are the first structurally characterized example of copper(i) clusters with telluroethers. Their different nuclearities and geometries can be attributed to the different donor atoms and chain flexibility in the ligands. The catalytic activities of six clusters were then investigated in the Ullmann C-N cross-coupling reaction and 2 displayed the best performance with a target product N-(4-phenyl)imidazole in 91.3% yield. From the viewpoint of structure, the specific steric acceptance around Cu(i) in 2 may allow imidazole and iodobenzene to stepwise coordinate with the copper center and give the target product effectively.