Syntheses and structures of missing links among polybromocyclopentadienyl rhenium and manganese tricarbonyl complexes

Complexes I-III are prepared by reactions of bromodiazocyclopentadienes C5H4 − nBrnN2 (n =  2, 3, 4) with BrM(CO)5 in CF3C6H5 at elevated temperatures. When the reaction of C5Br4N2 and BrRe(CO)5 is conducted at a lower temperature, the η1-pentabromocyclopentadienyl complex (η1-C5Br5)Re(CO)5 (IV) is isolated. All attempts to induce decarbonylation to the III are unsuccessful. The isomeric tribromo complex V is accessed via a debromination sequence.