Coordination and Ligand Substitution Chemistry of Bis(cyclooctyne)copper(I)

Cationic bis­(alkyne)­copper­(I) carbonyl and bis­(alkyne)­copper­(I) isocyanide complexes have been synthesized from the precursor (cyclooctyne)2CuBr. [Cu­(cyclo­octyne)2(CO)]­[SbF6] and [Cu­(cyclooctyne)2(CNtBu)]­[SbF6] have trigonal-planar and three-coordinate copper centers. The copper carbonyl complex [Cu­(cyclooctyne)2(CO)]­[SbF6] displays its C–O stretching frequency in the “nonclassical” metal carbonyl region (2171 cm–1), and the analogous copper­(I) isocyanide complex [Cu­(cyclooctyne)2(CNtBu)]­[SbF6] also has an unusually high CN stretching band at 2230 cm–1. The reaction of 3,5-Me2C6H3NH2 and 4-tBuC6H4NH2 with [Cu­(cyclooctyne)2(CO)]­[SbF6] led to CO displacement rather than addition to CO. CNtBu reacts with [Cu­(cyclooctyne)2(CO)]­[SbF6] to afford [Cu­(cyclooctyne)2(CNtBu)]­[SbF6]. The syntheses of [Cu­(cyclooctyne)­(CNtBu)2]­[SbF6] and [Cu­(CNtBu)4]­[SbF6] from the (cyclooctyne)2CuBr precursor are also reported.