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

A series of alkali metal 1‐adamantoxide (OAd1) complexes of formula [M(OAd1)(HOAd1)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 HOAd1 molecules was reduced. An X‐ray diffraction study of the sodium derivative shows that the complex features two unreduced HOAd1 donors as well as the reduced alkoxide (OAd1), with the Ad1 fragments clustered together on the same side of the NaO3 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(OAd1)(HOAd1)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 OAd1 groups. [ABSTRACT FROM AUTHOR]