Quinquevalent protactinium, niobium, and tantalum nitrates and nitrato-complexes

Abstract

Hexanitratoprotactinates(V), M^IPa(NO₃)₆(M^I= Cs, NMe₄, and NEt₄), have been prepared by reaction of the hexachloroprotactinates(V) with liquid dinitrogen pentoxide at room temperature. The niobium(V) and tantalum(V) hexachloro-analogues form oxytetranitrato-complexes, NMe₄M^VO(NO₃)₄(M^V= Nb and Ta), under similar conditions. Protactinium() halides react with fuming nitric acid, yielding the hydrated oxynitrate PaO(NO₃)₃,xH₂O (1 < x < 4) which is probably polymeric. Dinitrogen tetroxide reacts with protactinium(V) halides in anhydrous methyl cyanide to give the dimeric, solvated oxynitrate Pa₂O(NO₃)₈,2MeCN, whereas liquid dinitrogen pentoxide converts the pentahalides and freshly prepared hydroxide, but not the pentoxide, into the acid hexanitrato-complex HPa(NO₃)₆. Some chemical properties and the infrared spectra of the compounds are reported.