ROLE OF CU-] FORMAMIDIC ACID -] (AMINOHYDROXY)CARBENE ISOMERIZATIONS IN THE GAS-PHASE( ASSOCIATION ON THE FORMAMIDE )

The structures, relative stabilities, and bonding characteristics of c omplexes of formamide, formamidic acid, and (aminohydroxy)carbene with Cu+ have been investigated through the use of high-level density func tional theory (DFT) calculations. Geometries were optimized at the B3L YP/6-311G(d,p) level, while the final energies were obtained using a 6 -311+G(2df,2p) basis set expansion. Contrarily to what happens upon as sociation with alkali metal cations, the energy gaps between formamide and its two isomers decrease significantly upon Cu+ association, beca use formamidic acid and (aminohydroxy)carbene exhibit higher Cu+ bindi ng energies than formamide. This behavior is similar to the one exhibi ted in the protonation processes, indicating that the neutral-Cu+ inte ractions have a sizable covalent character. Nevertheless, the isomeriz ation processes among the systems studied (formamide, formamidic acid, (aminohydroxy)carbene) are not catalized by Cu+ ions, since in genera l the hydrogen transfers involved in such isomerization processes resu lt in a weakening of the interaction between the neutral and the metal cation. The only exception to this general behavior corresponds to th e isomerization between the nitrogen attached formamide complex and th e corresponding enolic species, because in this particular case the hy drogen shift enhances the ion-neutral interaction.