Reactions of Laser-Ablated Mg, Ca, Sr, and Ba Atoms with Hydrogen Cyanide in Excess Argon. Matrix Infrared Spectra and Density Functional Calculations on Novel Isocyanide Products

Laser-ablated alkaline earth metal atoms reacting with hydrogen cyanide in the presence of excess argon produce matrix-isolated linear metal isocyanides, MNC, but no noticeable amount of the corresponding cyanide isomer, MCN. Supplemental experiments with DCN show that, unlike the corresponding beryllium reactions, no products containing hydrogen are formed. Experiments with isotopically enriched H 13 CN yield MN 13 C shifted 40 cm -1 from MN 12 C in the C⋮N stretching frequency, with the isotopic shift virtually independent of the alkaline earth metal. As the mass of the group 2 metal increases, the C⋮N frequency decreases and the absorption becomes broader, the latter feature indicating a decreasingly rigid linear geometry. The lack of MCN indicates that the products form via attack of the energetic metal on the nitrogen atom, instead of through insertion into the C−H bond.