Abstract
The benzylidene complexes (CO) 5W=C(C 6H 4R- p)H (R = OMe ( 1), Me ( 2), H ( 3)) react with vinyl acetate ( 4a), ethyl vinyl ether ( 4b), 1-hexene ( 4c) and cyclopentene ( 6) by transfer of the benzylidene ligand to the CC bond of the olefin to give cyclopropanes. The reactions of 1 with these olefins and of 2 with vinyl acetate generally proceed according to an additive rate law consisting of three terms, e.g. -d[ 1]/d t = k 1[ 1] + k 2[ 1][olefin] + k 3[ 1]olefin] 2. The first and third order terms, however, deviate from zero only in the slow reactions and at very high concentrations of olefin. The influence of the solvent on the reaction rate is small. The activation parameters for the reaction of 1 with vinyl acetate are: Δ H★ = 42(1) kJ/mol and Δ S★ = − 143(3) J/(mol K). 2 reacts 3.8 times faster with vinyl acetate than 1. The cis/trans ratio of the cyclopropanes at high olefin concentration is independent of the olefin concentration and only slightly dependent on the polarity of the solvent. At low concentrations of olefin the reactions of 3 with 4c and 6, respectively, yield preferentially the trans-isomer in pentane and the cis-isomer in pentane/CH 2CL 2 solvent mixtures. The difference Δ S★( cis)- Δ S★( trans) is negative for all reactions investigated. For the reaction of 3 with 4a-c the cis/trans ratio increases with decreasing temperature, the difference Δ H★( cis) - Δ H★(trans) is in the range −0.73 to −6.0 kJ/mol.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
