Charge transfer, metal-carbonyl

It is believed that the primary step involves excitation of the acyl complex via a metal-to-terminal CO charge transfer (755). The molecule then loses CO and rearranges to the carbonyl alkyl, as shown in Eq. (43). However, it... 

The d-d transitions in most of the d6 metal carbonyls and cyanides are hard to locate with certainty, since the large A-values mean that metal-to-ligand charge transfer may occur at about the same energy as the two bands due to the tagf -) - eg(cr ) transition. For the complexes in which the metal furnishes fewer than 6 valence electrons (such as the d6 Fe(CN)e3 ), additional charge-transfer bands due to ligand-to-metal transitions further obscure the weak d-d bands.8 Nevertheless, in many cases reliable values for A are available for M(CO) and M(CN)6n complexes. These A-vahies are summarized in Tahle III. 

In the case of Pt-Fe, the two metals were suggested389,421 to be in the metallic state forming an alloy. EXAFS studies indicated an electron transfer from Fe to Pt, which allowed the conclusion that the aldehyde double bond is more easily adsorbed on the induced sites . In the case of Pt-Sn and Pt-Ge, the authors suggested that Snn+ or Gen+ ions (Lewis acids) activate the carbonyl group by enhancing the positive charge of the carbonyl carbon (equation 32). 

A different interpretation is favoured for the chromium on polyimide data by Jordan et al. [21], who propose that initial attack of chromium and charge transfer occurs on the carbonyl moiety. Since the charge transferred from the metal is distributed over the planar PMDA moiety of the polyimide, the core level spectra by themselves will not allow a distinction between the two models proposed. However, a careful analysis of the shake up features in the Cls, Ols and Nls core hole spectra might reveal the initial binding site when the amplitude distributions of the LUMO s and HOMO S in the system relative to the created core hole are considered. 

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