Migratory Insertion of Hydrogen Isocyanide in the Pentacyano(methyl)cobaltate(III) Anion

The preparation of the pentacyano(iminiumacetyl)cobaltate(III) anion and its N-methyl and N,N-dimethyl derivatives
is reported. The iminiumacetyl group is formed by migratory insertion of cis hydrogen isocyanide in the pentacyano(methyl)cobaltate(III) anion. The new compounds have been spectroscopically characterized by 1H, 13C, 15N, and
59Co NMR spectroscopy and by absorption spectroscopy. The iminium carbon atoms yield 13C NMR signals at
256.7, 247.7, and 240.4 ppm for the parent iminiumacetyl compound and its N-methyl and N,N-dimethyl derivatives,
respectively. The 15N resonance frequencies of the iminium groups and the lack of rotation of the carbon−nitrogen
bond both show that this bond is best described as a double bond. The structure of (Et4N)(Ph4As)2[Co(CN)5(CH3)]
was determined by X-ray crystallography at 122.0(5) K. The structure displays disorder.