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 = PPh(3), NCMe, NCPh, imines, ketones, Et(2)O, 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(eta(1)-O=C(Me)R)(CO)(3)(bipy)]BAr'(4) (R = CH(3), 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(Ctbd1;CR)(CO)(3)(bipy)] (R = Ph, 12; R = SiMe(3), 13). Complex 9 was found to catalyze the aziridination of benzylideneaniline with ethyl diazoacetate.