Metal carbonyls chemical analysis

General Methods. Methanol used in kinetic runs was distilled from sodium methoxide or calcium hydride in a nitrogen atmosphere before use. Freshly distilled cyclohexanol was added to the methanol in the ratio 6.0 ml cyclohexanol/200 ml MeOH and was used as an internal standard for gas chromatographic (GC) analysis. Benzaldehyde was distilled under vacuum and stored under nitrogen at 5°. Other aldehydes (purchased from Aldrich) were also distilled before use. The corresponding alcohols (purchased from Aldrich) were distilled and used to prepare GC standards. All metal carbonyl cluster complexes were purchased from Strem Chemical Company and used as received. Tetrahydrofuran (THF) was distilled from sodium benzophenone under nitrogen before use. 

Bodner and Gaul have examined the 13C-NMR spectra of a series of LNi(CO)3, LCr(CO)s, and (t)5-C5H5)Mn(CO)2L complexes (83). An analysis of the chemical shift for the para-phenyl resonance in phenyl-substituted ligands indicates that the electron-withdrawing character of the metal carbonyl fragment increases in the order Mn < Ni < Cr. 

Another feature which can be conveniently exploited by P NMR spectroscopy of metal carbonyl derivatives is the large effect on the chemical shift anisotropy of P resonances caused by the bonding mode of P donor atoms. The chemical shift anisotropies obtained by SSB analysis of P CP/MAS spectra in a series of PPh (n=l, 2, 3) ligands bonded to transition metal carbonyl complexes are strongly dependent on the coordination arrangement of the phosphorus atoms as shown in Figure 21. 

Figure 21 Chemical shift anisotropies obtained by spinning sideband analysis of CP/MAS spectra in a series of PPh (n = 1,2,3) ligands bonded to transition metal carbonyl complexes...

P. Macchi, A. Angelo Sironi. Chemical bonding in transition metal carbonyl clusters complementary analysis of theoretical and experimental electron densities. Coord. Chem. Rev. 238-239, 383 12 (2003). 

The x-ray photoelectron spectra for both dissolved and solventless polyamic acid have been reported in the literature [2-8], It has been noted previously by us [5-7], that the spectra for solventless PAA and PI exhibit a pronounced deficiency for the Cls and Ols carbonyl emission. This, together with an analysis of the Nls lineshape and the Ols and Cls shake up features, allows us to derive conclusions on the chemical nature of solventless polyamic acid and to explain it s high reactivity towards metals as discussed below. 

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