Technetium magnetic susceptibility

Organometalhc complexes of technetium-99 can be studied by the traditional physical tools used in chemistry. Techniques hke infrared, multinuclear magnetic resonance, and mass spectroscopies, as well as magnetic susceptibility (to determine the number of unpaired electrons and thus the oxidation state) and X-ray crystallography are the main methods to study these complexes. X-ray diffraction methods are particularly important since only one small crystal is needed to determine the complete structure of the compound. 

The coordination chemistry involves the oxidation states from -i-7 to -1. Coordination numbers from 4 to 9 are known. Crystal field considerations and magnetic susceptibility measurements show that technetium forms low-spin compounds. Dinuclcar complexes frequently display metal to metal bond character. There is some evidence that technetium complexes are thermodynamically less stable and kinctically more reactive than the corresponding complexes of rhenium. A multitude of coordination compounds of technetium has been synthesized and unambiguously characterized. Investigations of the complex chemistry have been enormously stimulated by the development of Tc radiopharmaccuticals. 

A total of seven valence electrons are available for bonding. Compounds of technetium in the formal oxidation states from +7 to -1 have been synthesized. Tc (d°) is verified for example by rc04. An example of the -1 oxidation state is the pentacar-bonyl anion [Tc(CO)5 [6], but no structure determination or magnetic susceptibility measurement have been reported. 

Much attention was paid to slruelures, superconducting properties, magnetic susceptibilities, Knight shifts, and specific heats of intermetallic compounds of technetium. Their structure types and lattice constants arc presented in Table 9.3. A. 

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