Reaction of Cp*(CO)₂Re=Re(CO)₂Cp* with alkynes produces dimetallacyclopentenones Cp*(CO)₂Re(μ-η¹,η ³-CR=CR′CO)Re(CO)Cp* which react with acid to form cationic bridging vinyl complexes

Cp*(CO)₂Re=Re(CO)₂Cp* (1) reacted with terminal alkynes HC≡CR (R = H, CH₃, C₆H₅, C(CH₃)=CH₂, OCH₂CH₃) to produce dimetallacyclopentenones Cp*(CO)₂Re(μ-η¹,η ³-CH=CRCO)-Re(CO)Cp* (4-8). The reaction of 1 with alkynes having one ester substituent also gave dimetallacyclopentenones. Reaction of 1 with HC≡CCO₂Me gave Cp*(CO)₂Re[μη¹,η³-CH=C(CO ₂CH₃)CO]Re(CO)Cp* (9) and with CH₃C≡CCO₂Me gave Cp*(CO)₂Re[μ-η¹,η³-(CO ₂-CH₃)C=C(CH₃)CO]Re(CO)Cp* (10). At low temperature, the η²-propyne complex Cp*(CO)₂-Re(μ-CO)Re(CO)(HC≡CCH₃)Cp* (12) and Cp*(CO)₂Re[μ-η¹,η³-C(CH ₃)=CHCO]Re(CO)Cp* (11) were observed as intermediates in the formation of Cp*(CO)₂Re[μ-η¹,η ³-CH=C(CH₃)-CO]Re(CO)Cp* (5). Protonation of dimetallacyclopentenone 2 with CF₃CO₂H produced [Cp*(CO)₂Re(μ-η¹,η²-CH=CH ₂)Re(CO)₂Cp*]⁺CF₃CO ₂^- (14), a species with a bridging vinyl group. Protonation of the thermodynamically favored regioisomeric dimetallacyclopentenone 5 gave [Cp*(CO)₂Re(μ-η¹,η ²-(E)-CH=CHCH₃)Re(CO)₂Cp*] ⁺CF₃CO₂^- (15). Protonation of kinetically formed regioisomeric dimetallacyclopentenone 11 at low temperature gave [Cp*-(CO)₂Re(μ-η¹,η²-CCH ₃=CH₂)Re(CO)₂Cp*]⁺CF ₃CO₂^- (16).