Rhenium magnetic susceptibility

Rhenium metal exhibits a very low paramagnetism which is field-independent and almost temperature-independent. In the range 79—471 K, magnetic susceptibility data for two independent samples were shown to correspond, when Tis in Kelvin, to the following equations (5) ... 

The crystal structure of cadmium rhenium(V) oxide, as determined by single-crystal technique,1 is of the face-centered cubic pyrochlore type (a = 10.219 A.). The only positional parameter for the 48 (/) oxygens is x = 0.309 0.007 when rhenium is at the origin. The density, determined pycnometrically, is 8.82 0.03 g./cc., compared with the theoretical value of 8.83 g./cc. for Z = 8. The resistivity between 4.2 K and room temperature is very low (10-3-10-4 J2-cm.) and has a positive temperature coefficient. Over the same temperature range the magnetic susceptibility is low and temperature-independent. These properties indicate that cadmium rhenium(V) oxide exhibits metallic conductivity. 

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. 

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