REACTION OF CP-ASTERISK(CO)(2)RE=RE(CO)(2)CP-ASTERISK WITH ALKYNES PRODUCES DIMETALLACYCLOPENTENONES )(2)RE(MU-ETA(1),ETA(3)-CR=CR'CO)RE(CO)CP-ASTERISK WHICH REACT WITH ACID TO FORM CATIONIC BRIDGING VINYL COMPLEXES

Cp(CO)(2)Re=Re(CO)(2)Cp* (1) reacted with terminal alkynes HC=CR (R = H, CH3, C6H5, C(CH3)=CH2, OCH2CH3) to produce dimetallacyclopentenone s Cp(CO)(2)Re(mu-eta(1),eta(3)-CH=CRCO)Re(CO)Cp* (4-8). The reaction of 1 with alkynes having one ester substituent also gave dimetallacycl opentenones. Reaction of 1 with HC=CCO(2)Me gave CO)(2)Re[mu-eta(1),et a(3)-CH=C(CO2CH3)CO]Re(CO)Cp (9) and with CH3C=CCO(2)Me gave 2)Re[mu- eta(1),eta(3)-(CO2CH3)C=C(CH3)CO]Re(CO)Cp (10). At low temperature, t he eta(2)-propyne complex Cp(CO)(2)Re(mu-CO)Re(CO)(HC=CCH3)Cp* (12) a nd p(CO)(2)Re[mu-eta(1),eta(3)-C(CH3)=CHCO]Re(CO)Cp* (11) were observ ed as intermediates in the formation of p(CO)(2)Re[mu-eta(1),eta(3)-C H=C(CH3)CO]Re(CO)Cp (5). Protonation of dimetallacyclopentenone 2 wit h CF3CO2H produced mu-eta(1),eta(2)-CH=CH2)Re(CO)(2)Cp](CF3CO2-)-C-(14), a species with a bridging vinyl group. Protonation of the thermo dynamically favored regioisomeric dimetallacyclopentenone 5 gave (1),e ta(2)-(E)-CH=CHCH3)Re(CO)(2)Cp](CF3CO2-)-C-+ (15). Protonation of kin etically formed regioisomeric dimetallacyclopentenone 11 at low temper ature gave -eta(1),eta(2)-CCH3=CH2)Re(CO)(2)Cp](CF3CO2-)-C-+ (16).