Geometries and electronic structures of group 10 and 11 metal carbonyl cations, [M(CO)_n]^x+ (M^x+ = Ni²⁺, Pd²⁺, Pt²⁺, Cu⁺, Ag⁺, Au⁺; n = 1-4)

The geometry and electronic structure of group 10 and 11 metal carbonyl cations, [M(CO)_n]^x+ (M^x+ = Ni²⁺, Pd²⁺, Pt²⁺, Cu⁺, Ag⁺, Au⁺; n = 1-4), were examined by the hybrid density functional method (B3LYP) and the coupled cluster method (CCSD(T)). For group 10 metals, monocarbonyl cations have C_∞v structures, dicarbonyl cations have D_∞h and C_2ν structures, and tri- and tetracarbonyl cations have C_2v and D_4h structures, respectively. Group 11 metal carbonyl cations have C_∞v, D_∞h, D_3h, and T_d structures for mono-, di-, tri-, and tetracarbonyls, respectively. The (CO)_n-1M^x+-CO dissociation energies D₀ (CO) of group 10 metal carbonyl cations are significantly larger than those of group 11 metal carbonyl cations. Group 10 metal tetracarbonyl cations are still stable, while for group 11 metals, D₀ (CO) is significantly reduced in going from dicarbonyls to tri- and tetracarbonyls. The vibrational frequencies v(CO) are higher by 110-165 cm^-1 for group 10 metal complexes and by 45-115 cm^-1 for group 11 metal complexes than that for free CO (2143 cm^-1).