Isomer differentiation by tri-osmium cluster complexation of substituted 1,3-cyclohexadienes

Abstract

A series of methyl- and dimethyl-substituted 1,3-cyclohexadienes have been prepared from their aromatic analogues via Birch reduction and subsequent isomerisation with Fe(CO) 3 fragments. These ligands were reacted with [Os 3(CO) 10(CH 3CN) 2] to form tri-osmium decacarbonyl cluster compounds containing the η 4-coordinated substituted 1,3-cyclohexadienes. The various isomers of the substituted dienes show a dramatic difference in their reactivity towards the tri-osmium cluster and it is likely that this is due to the steric interactions between the methyl substituents and the cluster framework, with this effect being more marked for the di-substituted ligands.