Reactivities of Some Unsaturated Hydrocarbons with the Half-Sandwich Complex [Re(η⁶-C₆H₆)(NCCH₃)₃]⁺

The CH3CN ligands in the semisolvated complex [Re(η6-C6H6)(NCCH3)3]+ exchange on a seconds time scale, which facilitates substitution reactions with alkynes and alkenes. The reaction of [Re(η6-C6H6)(NCCH3)3]+ with the alkyne dimethyl acetylenedicarboxylate (C6H6O4) led via C–C coupling to the ReIII complex [Re(η6-C6H6)(κ2-C12H12O8)(NCCH3)2]+, incorporating a metallacyclopentadiene moiety. Some [2+2+2] cycloaddition products were observed in small amounts when treating the diyne 1,6-heptadiyne with catalytic amounts of [Re(η6-C6H6)(NCCH3)3]+. The monosubstituted ReI complex [Re(η6-C6H6)(η2-C4H2O3)(NCCH3)2]+ formed with maleic anhydride (C4H2O3). The reaction of [Re(η6-C6H6)(NCCH3)3]+ with allyl bromide leads to oxidative addition of the latter, yielding a mixture of [Re(η6-C6H6)(η3-C3H5)(NCCH3)xBr2–x]x+ (x = 0–2). The product ratio is influenced by the reaction conditions. In CH3CN, [Re(η6-C6H6)(NCCH3)3]+ does not react with arenes. In acetone, the formation of bis-arene complexes via the intermediate [Re(η6-C6H6)(acetone)2(NCCH3)]+ occurs and is exemplified with the synthesis of [Re(η6-C6H6)(η6-ibuprofen)]+.