How do the nucleophilicity and size of an isocyano carbon atom differ from those of a cyano nitrogen atom?

Abstract

Hydrogen-bond stretching force constants k_σ and distances r(B ⋯ X) from the rotational spectra of the C_3v dimers B ⋯ HX, where B = CH₃NC or CH₃CN and X = F, Cl, CN or CCH, have been used to establish the difference in magnitude of the gas-phase nucleophilicity and of the van der Waals radius between the isocyano carbon atom in CH₃NC and the cyano nitrogen atom in CH₃CN.