Inhibition of Alkali Metal Reduction of 1-Adamantanol by London Dispersion Effects.

A series of alkali metal 1-adamantoxide (OAd 1 ) complexes of formula [M(OAd 1 )(HOAd 1 ) 2 ], where M=Li, Na or K, were synthesised by reduction of 1-adamantanol with excess of the alkali metal. The syntheses indicated that only one out of every three HOAd 1 molecules was reduced. An X-ray diffraction study of the sodium derivative shows that the complex features two unreduced HOAd 1 donors as well as the reduced alkoxide (OAd 1 ), with the Ad 1 fragments clustered together on the same side of the NaO 3 plane, contrary to steric considerations. This is the first example of an alkali metal reduction of an alcohol that is inhibited from completion due to the formation of the [M(OAd 1 )(HOAd 1 ) 2 ] complexes, stabilized by London dispersion effects. NMR spectroscopic studies revealed similar structures for the lithium and potassium derivatives. Computational analyses indicate that decisive London dispersion effects in the molecular structure are a consequence of the many C-H⋅⋅⋅H-C interactions between the OAd 1 groups.