Quadrupole splitting structure determination from

Apart from the determination of the structures of stannylenes by diffraction methods (X-ray or electron diffraction) many other physico-chemical techniques can be exployed to characterize these compounds more completely. Besides the classical methods such as IR-, Raman-, PE-, UV- and NMR-spectroscopy, MoBbauer-119 m-tin spectroscopy is widely used for the determination of the oxidation states of tin atoms and of their coordination 1n8-12°-123>. jt is not in the scope of this report to study the dependence of MoBbauer constants such as isomer shift and quadrupole splitting on structural parameters. Instead, we want to concentrate on one question Which information can we deduce from the structure of stannylenes to evaluate their reactivity ... 

As indicated in the previous discussion, Mossbauer spectroscopy provides information that when coupled with results using other structural techniques assists in determining the structure of the complex under analysis. The relationships between the various techniques are summarized in Table II. The Mossbauer chemical shift provides information about the 4 electron contribution to the bond between the metal and the ligands in a complex. Similar estimates can be obtained from the results of measurements on the fine structure in the x-ray absorption edge and nuclear magnetic resonance data. The number of unpaired electrons can be evaluated from magnetic susceptibility data, electron spin resonance, and the temperature coeflScient of the Mossbauer quadrupole splitting (Pr). 

The QS in the Fe Mdssbauer spectra is determined by the geometry of the iron(II) coordination polyhedron and has been utilized to gain information on the structure of the complexes from the spectral parameter vs structure correlation. Conversely, the data available on the structure of clathrochelates employed for working out a modern version of the partial quadrupole splitting (PQS) concept permits one to obtain absolute PQS values and to analyse the results for macrobicyclic complexes [264, 265]. 

The temperature dependence of the quadrupole splitting of Tm in TmES yielded an estimate of the values of the CEF parameters for the Tm ion in the ethylsulfate structure. Since optical absorption spectroscopy had previously furnished estimates of the four parameters needed to characterize the CEF in this structure [Wong and Richman (1961)], their determination in this case provided a valuable cross-check on the validity of the method which has been outlined in section 2.1.3. The experiments also revealed a substantial shielding of the 4f electrons from the crystal field, as has been described for the case of thulium metal in section 2.1.3. 

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