Stereoisomerism of bis(σ-Zincane) Complexes: Evidence for an Intramolecular Pathway.
The first bis(σ-zincane) complexes, heterotri- metallic species [M(CO)4(η2-HZnBDI)2], have been prepared (BDI=κ2-{2,6-(iPr)2C6H3NCMe}2CH). For M=Cr, a single stereoisomer is observed in solution and the solid-state. For M=Mo and W, cis and trans isomers were found to reversibly interconvert at 297 K. Despite the huge steric demands of the ligand on zinc, the cis isomer was found to be the most thermodynamically stable in all cases. The activation parameters for the isomerisation when M=Mo are ΔH≠=20.8 kcal mol-1and ΔS≠=-12.8 cal K-1mol-1. In combination with DFT calculations, the negative activation entropy suggests an intramolecular rotation mechanism for isomerisation.
Department of Chemistry, Imperial College London, South Kensington, London, SW7 2AZ, UK.
Olga
O
Ekkert
Department of Chemistry, Imperial College London, South Kensington, London, SW7 2AZ, UK.
Andrew J P
AJP
White
Department of Chemistry, Imperial College London, South Kensington, London, SW7 2AZ, UK.
Mark R
http://orcid.org/0000-0002-9339-9182
MR
Crimmin
isomerisation; mechanism; reaction pathways; zinc hydride; σ-complexes