Intercalation of Hexagonal Boron Nitride by Strong Oxidizers and Evidence for the Metallic Nature of the Products

Hexagonal boron nitride, h-BN, is intercalated, at ∼20°C, by S2O6F2 (the source of the powerfully oxidizing SO3F• radical) to give a deep blue solid (BN)∼3SO3F, which is a temperature-independent paramagnet (xg≈55.2×10−6 cgs units). Four probe conductivity measurements on an intercalated piece of highly oriented pyrolytic BN (HOPBN) have established an approximate doubling of the conductivity with temperature decrease from 295 to 77 K. The low conductivity (σ295K=1.5 S cm−1) is attributed to high effective carrier mass deriving from poor pπN–pπB overlap and consequent narrow band character. The conductivity at 295 K of a graphite relative of composition C∼8.5SO3F made from a HOPG chip was found to be 1.1×105 S cm−1, and at 77 K it was found to be 3.1×105 S cm−1. Other blue, poorly conductive h-BN intercalation compounds have been obtained using SbF5/F2 mixtures on h-BN, and from AsF5 on (BN)∼3SO3F, but they are of unknown composition.