Editing Protactinium (section)

===Other inorganic compounds===
Oxyhalides and oxysulfides of protactinium are known. PaOBr<sub>3</sub> has a monoclinic structure composed of double-chain units where protactinium has coordination 7 and is arranged into pentagonal bipyramids. The chains are interconnected through oxygen and bromine atoms, and each oxygen atom is related to three protactinium atoms.<ref name="pabr5b" /> PaOS is a light-yellow, non-volatile solid with a cubic crystal lattice isostructural to that of other actinide oxysulfides. It is obtained by reacting protactinium(V) chloride with a mixture of [[hydrogen sulfide]] and [[carbon disulfide]] at 900&nbsp;°C.<ref name="pao2" />

In hydrides and nitrides, protactinium has a low oxidation state of about +3. The hydride is obtained by direct action of hydrogen on the metal at 250&nbsp;°C, and the nitride is a product of ammonia and protactinium tetrachloride or pentachloride. This bright yellow solid is thermally stable to 800&nbsp;°C in vacuum. Protactinium carbide (PaC) is formed by the reduction of protactinium tetrafluoride with barium in a carbon crucible at a temperature of about 1400&nbsp;°C.<ref name="pao2" /> Protactinium forms [[borohydride]]s, which include Pa(BH<sub>4</sub>)<sub>4</sub>. It has an unusual polymeric structure with helical chains, where the protactinium atom has coordination number of 12 and is surrounded by six BH<sub>4</sub><sup>−</sup> ions.<ref name="g1277">[[#Greenwood|Greenwood]], p. 1277</ref>