Intramolecular hydroamination of 6-aminohex-1-yne catalyzed by Lewis acidic rhenium(I) carbonyl complexes

With the aim to determine the effect of Lewis acidity of rhenium(I) carbonyl complexes on their catalytic properties, and to develop more efficient catalysts based on Re(I) carbonyl systems, a series of rhenium(I) carbonyl triflate complexes with various degrees of Lewis acidity was investigated. Pyridine-substituted bromo tricarbonyl rhenium(I) complexes of the type fac-[ReBr(CO)3L2] (L = py-Cl, py, py-Me and py-NMe2) were synthesized from [ReBr(CO)5] using trimethylamine N-oxide (TMNO) as decarbonylating agent. The complexes [ReBr(CO)5] and fac-[ReBr(CO)3L2] were then reacted with silver triflate to yield the complexes [Re(CF3SO3)(CO)5] and fac-[Re(CF3SO3)(CO)3L2]. The synthesis and characterization of these complexes and their application in the catalysis of the cyclization of 6-aminohex-1-yne are discussed. The crystal structure of [Re(CF3SO3)(CO)3(py)2] is also presented.