Phenylsodium Compounds with η³‐Allyl or η⁶‐Phenyl Coordination

In spite of the identical negative charge available, phenyl-substituted allyl anions can be coordinated differently by counter ions. Thus the Na(pmdta)⊕ (pmdta = pentamethyldiethylenetriamine) ion coordinates in a η3 manner to the allyl system in 1, but in a η6 manner to the phenyl ring in 2. Apparently the energy surface for the migration of the cation over the planar carbanion in 2 contains no large energy barriers and for steric reasons the Na(pmta)⊕ ion avoids coordinating with the allyl system of the cyclohexenyl unit.