Synthesis of rhenium(V) 2,4,6-trimethylbenzylidyne complexes by abstracting O2- from an acyl with triflic anhydride

Article abstract of DOI:10.1021/om00017a080

Re[C(O)Ar′](CO)₅ (Ar′ = 2,4,6-C₆H₂Me₃; 1) can be prepared in 55% yield by adding Ar′C(O)Cl to [Re(CO)₅]^-. Addition of trifluoromethanesulfonic anhydride to 1 in dichloromethane yields off-white [Re-(CAr′)(CO)₄(OTf)](OTf) (2) quantitatively. Three equivalents of tetraethylammonium chloride reacts with 2 in dichloromethane to give [Et₄N][Re(CAr′)(CO)₂Cl₃] (3), which when treated with TlBF₄ in the presence of pyridine affords lemon yellow Re(CAr′)(CO)₂Cl₂(py) (4). A slurry of 2 in dichloromethane also reacts cleanly with a THF solution of LiO-2,6-C₆H₃-i-Pr₂ (LiOAr) to yield blood red Re(CAr′)(CO)₂(OAr)₂(THF) (5a) in 80% isolated yield. Addition of pyridine to 5a yields an analogous six-coordinate pyridine adduct (5b). Addition of pinacol to 2 followed by triethylamine yields yellow, pentanesoluble Re(CAr′)(CO)₂(O₂C₂Me₄) (6a). Although 6a shows no tendency to bind THF, it reacts with pyridine to yield Re(CAr′)(CO)₂(O₂C₂Me₄)(py) (6b) quantitatively. Addition of triphenylphosphine to 6a produces dark red Re(CAr′)(CO)(O₂C₂Me₄)(PPh₃) (6c).