Synthesis and reactions of the rhenium fulvene complexes [Re(η6-C5Me4CH2)(CO)2(C6F4R)] (R = F or CF3): products derived from initial C–F activation

Abstract

The UV irradiation of [Re(η5-C5Me5)(CO)3] in the presence of C6F6 effected intermolecular C–F and intramolecular C–H activation generating [Re(η6-C5Me4CH2)(CO)2(C6F5)] 1a in two isomeric forms. In the major isomer the CH2 group lies trans to the C6F5 group both in solution and in the crystal. In the minor isomer the CH2 lies cis to the C6F5 group. A similar reaction with C6F5CF3 generates [Re(η6-C5Me4CH2)(CO)2(C6F4CF3)] 1b in four isomeric forms. In the major form the CF3 group is in the 4 position and the CH2 group lies trans to the C6F4CF3 group. The other three isomers are formed by rotation of the η6-C5Me4CH2 ligand as above, by placing the CF3 at the 3 position, and by a combination of the two. Complex 1a reacted with PMe3 to form the zwitterionic complex [Re(η5-C5Me4CH2PMe3)(CO)2(C6F5)] and with MeO– to form the anion [Re(η5-C5Me4CH2OMe)(CO)2(C6F5)]–, isolable as the NEt4+ salt. The reaction of 1a with HX (X = Cl or Br) generated cis-[Re(η5-C5Me5)(CO)2(C6F5)X] initially. More prolonged reaction led to the trans isomers. On reaction with HI, only the trans isomer was formed. Reaction of 1a with HBF4 in Et2O in the presence of MeCN led to formation of the salt [Re(η5-C5Me5)(CO)2(C6F5)(NCMe)]+[BF4]–. The halogens Cl2, Br2 and I2 reacted to form (halogenomethyl)tetramethylcyclopentadienyl complexes trans-[Re(η5-C5Me4CH2X)(CO)2(C6F5)X] (X = Cl, Br or I). The bromo complex has been characterized crystallographically.