New Synthetic Routes to Cationic Rhenium Tricarbonyl Bipyridine Complexes with Labile Ligands

Triflate abstraction from the complex [Re(OTf)(CO)3(bipy)] (1) using the salt NaBAr‘4 (Ar‘ = 3,5-bis(trifluoromethyl)phenyl) in dichloromethane solution in the presence of L = PPh3, NCMe, NCPh, imines, ketones, Et2O, THF,
MeOH, and MeI affords cationic complexes [Re(L)(CO)3(bipy)]+ as their BAr‘4- salts. The new complexes have
been characterized spectroscopically and, for [Re(η1-OC(Me)R)(CO)3(bipy)]BAr‘4 (R = CH3, 6a; R = Ph, 6b),
and [Re(THF)(CO)3(bipy)]BAr‘4 (9), also by single-crystal X-ray diffraction. Compared with conventional methodologies,
the route reported here allows the coordination of a broader range of weakly coordinating ligands and requires
considerably milder conditions. On the other hand, the reactions of lithium acetylides with [Re(THF)(CO)3(bipy)]BAr‘4 (9) can be used for the high-yield syntheses of rhenium alkynyls [Re(C⋮CR)(CO)3(bipy)] (R = Ph, 12; R =
SiMe3, 13). Complex 9 was found to catalyze the aziridination of benzylideneaniline with ethyl diazoacetate.