The impact of external pressure on the ReO3-type structure and the electronic properties of NbO2-xF1+x has also been explored. Anionic control over the cubic to rhombohedral phase transition is predicted with a maximum transition pressure of 5 GPa for x = 0.35. The trigonal octahedral distortion expected in NbF3 is found to produce a spin-polarised semiconducting phase rather than the previously predicted half-metallic cubic phase. The cubic to rhombohedral phase transition is also found to be the driving force behind half-metallicity in compositions around x = 0.35. This is caused by a narrowing of the Nb 3d t2g band as a result of octahedral tilting. This structural control over half-metallicity could potentially be exploited to give materials that could be switched between metallic and half-metallic states under moderate applied pressure. Such behaviour would present a new approach in controlling spin currents for spintronic devices.