Reduction of thulium-, samarium- and ytterbium halides till divalent state in hexamethylphosphorustriamide solutions

Chlorides, bromides, and iodides of ytterbium, samarium, and thulium have been reduced in solutions of hexamethylphosphorustriamide by the action of metal sodium in an argon atmosphere. It has been established from kinetic data on oxidation of bromides of bivalent, ytterbium, samarium and thulium that stability of bivalent forms decreases from ytterbium to thulium. The periods of half-oxidation at 25 deg C have following values: 31 hr (Yb), 2 hr (Sm), 11 min (Tm). Electron absorption spectra have been recorded for solutions of some halogenides of samarium (2) and ytterbium (2) and for thulium (2) bromide in hexamethylphosphorustriamide. It has been shown that a shift of the absorption bands for various halogenides of samarium(2) and ytterbium(2) is in accordance with a known spectrochemical series: NO3-> N3- (C6H5)3PO approximately hexamethylphosphorustriamide > Cl- > Br- > Isub(-)