Quinquevalent protactinium and quadrivalent actinide tropolonates

Abstract

Protactinium pentachloride, pentabromide, and oxide tribromide react with an excess of tropolone in nonaqueous solvents to yield tetrakis(tropolonato)protactinium(V) halides of the type Pa(trop)₄X (trop = C₇H₅O₂^–; X = CI or Br). Attempts to prepare Pa(trop)₅ have been unsuccessful. Reactions in ethanol involving lithium tropolonate and the tetrakis(tropolonato)metal(V) halides, or Pa(trop)₄ and tropolone, result in the precipitation of Pa(trop)₄OEt, which on the addition of hydrochloric acid–acetone mixtures is converted into Pa(trop)₄CI. This forms a 1 : 1 adduct Pa(trop)₄CI,DMSO with dimethyl sulphoxide but does not react with dimethylformamide. The quadrivalent tropolonates Pa(trop)₄, Np(trop)₄, and Pu(trop)₄ have been prepared by reactions in either aqueous or non-aqueous solvents. Pa(trop)₄, but neither Np(trop)₄, nor Pu(trop)₄ reacts with lithium tropolonate to form a pentakis-complex. Oxidation of Pa(trop)₄ in perchloric acid solution yields Pa(trop)₄CIO₄. Some chemical properties, i.r. spectra and crystallographic results are reported for these compounds and for some quadrivalent thorium tropolonates.