Preparation and spectral properties of actinide(IV)--hexaiodo complexes

Hexaiodo complexes of the type R$sub 2$M/sup IV/I$sub 6$ (R = NEt$sub 4$, NMe$sub 3$Ph; M/sup IV/ = Th, Pa, U) have been prepared by reactions in oxygen-free, anhydrous methyl cyanide. Ir and Raman data are reported together with electronic spectral results for the protactinium(IV) and uranium(IV) complexes. Ligand field and spin--orbit coupling constants derived for the hexaiodoprotactinates(IV) are discussed in relationship to values obtained earlier for other hexahalogenoprotactinates(IV), (NEt$sub 4$)$sub 2$PaX$sub 6$ (X = F, Cl, Br). (auth)