Theoretical Study of Copper-Carbonyls Interaction in Cu(co)n (N=1-2) Complexes

The copper carbonyl complexes revisited: Why are the infrared spectra and structures of copper mono and dicarbonyl so different?

“…Note that the relationship X 11 / X 13 = 4 , true in the limit of the local mode model developed by Mills and Robiette [27], holds here only approximately, showing that ν 1 and ν 3 are not purely carbonyl stretching motions, but vibrations in which carbonyl and metalcarbon stretching motions are notably coupled. This also shows when examining the isotopic effects on ν 3 , with a 12 C/ 13 C shift larger than the 16 O/ 18 O one, in spite of a smaller change in reduced mass, another sign of coupling [28]. Assignment of the weak band at 2542.5 cm -1 to the ν 1 + ν 4 transition would place the ν 4 , Σ u symmetry band around 490 cm -1 .…”

“…Assignment of the weak band at 2542.5 cm -1 to the ν 1 + ν 4 transition would place the ν 4 , Σ u symmetry band around 490 cm -1 . In fact, in the low frequency region, a very weak band is observed near 493 cm-1 (figures 5 and 7), with a notably larger 16 O/ 18 O shift ( -10.7 cm -1 ) than 12 C/ 13 C (-3.5 cm -1 ) , which can thus be assigned to the ν 4 mode. Further below, a much stronger band is observed near 247 cm -1 , with a large 12 C/ 13 C (-7.2 cm -1 ) and a small 16 O/ 18 O (-1.9 cm -1 ) isotopic effects, as expected for a Cu-C=O bending mode, which must involve the cis-C-C=O bending coordinate.…”

“…In fact, in the low frequency region, a very weak band is observed near 493 cm-1 (figures 5 and 7), with a notably larger 16 O/ 18 O shift ( -10.7 cm -1 ) than 12 C/ 13 C (-3.5 cm -1 ) , which can thus be assigned to the ν 4 mode. Further below, a much stronger band is observed near 247 cm -1 , with a large 12 C/ 13 C (-7.2 cm -1 ) and a small 16 O/ 18 O (-1.9 cm -1 ) isotopic effects, as expected for a Cu-C=O bending mode, which must involve the cis-C-C=O bending coordinate. Another band is, however, observed near 610 cm -1 with the same isotopic behaviour and, yet, about 15% of the intensity of the former, thus very unusually strong for a combination or overtone transition.…”

“…In their theoretical paper on the mono-and dicarbonyl, Ceron and Mendizabal showed that the stability of the copper-monocarbonyl could be perfectly explained by calculating the induction and dispersion contributions [16]. Consequently, the causes of the failure of the density functional -based methods, not taking into account correctly the dispersion energy, can be understood.…”

“…In 1995, V. Barone, using various DFT-based calculations, predicted the electronic structures, energies, geometries and some spectroscopic vibrational properties of the CuCO, Cu(CO) 2 and Cu(CO) 3 series [15], predicting remarkably well the bent structure of CuCO and that Cu(CO) 2 should revert to linearity with a 2 Π ground state. Even more recently, Cerón and Mendizabal examined in detail for the first time using high level ab initio methods, ranging from MP2 to CCSD(T), the reasons for the change in bonding strength when going from CuCO to Cu(CO) 2 [16] . In particular, they showed that the low stability of the copper-monocarbonyl [17] could be perfectly explained by calculating the induction and dispersion contributions, at the highest level of theory.…”