Protonation of rhenium 1,3-enyne and 1,3-diyne complexes: formation of exo-alkylidene η3-allyl and η3-propargyl complexes

Protonation of η2-enyne rhenium complex C5Me5(CO)2Re(η2-3,4-trans-PhCCCHCHPh) (24) occurred at the coordinated alkyne to produce 1-metallacyclopropene complex C5Me5(CO)2Re[η2-trans-(PhHCCH)CCHPh]+BF4 − (26), instead of protonation at the non-coordinated alkene to produce an η3-propargyl complex. Protonation of the alkene coordinated η2-enyne rhenium complex C5Me5(CO)2Re(η2-1,2-cis-PhHCCHCCPh] (25) occurred at the non-coordinated alkyne to produce exo-alkylidene η3-allyl complex C5Me5(CO)2Re(η3-exo,anti-CHPhCHCCHPh)+BF4 − (27), instead of protonation at the coordinated alkene to produce an η3-propargyl complex. Protonation of η2-diyne complex C5Me5(CO)2Re(η2-CH3CCCCCH3) (32) at −78 °C produced the rhenium hydride complex trans-C5Me5(CO)2ReH(η2-CH3CCCCCH3)+BF4 − (33), which was converted to exo-alkylidene η3-propargyl complexes C5Me5(CO)2Re[η3-(CH3CH)CCCCH3]+BF4 − (34a and 34b) at 0 °C.