Matrix Infrared Spectroscopic and Theoretical Investigations of M···NCCN, M···CNCN, M···C(N)CN, NCMCN, CNMNC, CNMCN, and [M···NCCN]+ Produced in the Reactions of Group 11 Metal Atoms with Cyanogen.

Reactions of group 11 metals with cyanogen, N≡C-C≡N, in excess argon and neon have been carried out, and the products were identified via examination of the matrix spectra and their variation upon photolysis, annealing, and isotopic substitutions. Density functional theory calculations provided helpful information for the plausible products and reaction paths. While M···NCCN and M···CNCN were observed in all three metal systems, the cyanide and isocyanide products (NCMCN, NCMNC, and CNMNC) were identified only in the Cu reactions, and M···C(N)CN was identified in the Cu and Au spectra. Intrinsic reaction coordinate calculation results along with the observed spectral variation upon photolysis and annealing suggest that Cu···C(N)CN was the pathway to cyanide and isocyanide. The product absorptions with exceptionally high C-N stretching frequencies in the Au system have been tentatively assigned to a cation [Au···NCCN+]. The group 11 metal cyanides and isocyanides that require two chemical bonds to the central metal are energetically favorable only in the lightest metal system.