Acid-Catalyzed Isomerization of Rhenium Alkyne Complexes to Rhenium Allene Complexes via 1-Metallacyclopropene Intermediates

摘要: The alkyne complexes C{sub 5}Me{sub 5}(CO){sub 2}Re({eta}{sup 2}-MeC{triple_bond}CMe) (1) and 5}H{sub (6) underwent acid-catalyzed isomerization by way of 1-metallacyclopropene intermediates to form the allene 2}-2,3-MeHC{double_bond}C{double_bond}CH{sub 2}) (5) (7). Stoichiometric reaction 1 with CF{sub 3}CO{sub 2}H initially produced kinetic addition product 2}Re[{eta}{sup 2}-(Z)-MeHC{double_bond}CMeO{sub 2}CCF{sub 3}] (8-Z), which slowly isomerized thermodynamically more stable E isomer 8-E. 6 at {minus}73 C only 2}-(E)-MeHC{double_bond}CMeO{sub (9-E), -60 a 80:20 equilibrium mixture 9-E 9-Z. Treatment 9-Z base led formation complex 7. rate this elimination was independent concentration. Labeling studies showed that intermediate 2}({eta}{sup 2}-CMeCHMe){sup +}CF{sub 2}{sup {minus}} (12-CF{sub undergoes number important reactions include, in order decreasing relative rates: trifluoroacetate give enol complexes, (2) deprotonation complexed allenes, (3) degenerate 1,2-hydride migrations, (4) hydride migrations {eta}{sup 3}-allyl tomore » alkynes.« less