copic niobium tetrafluoride (NbF4) and niobium tetrachloride (NbCl4). While the trihalogen compounds can be obtained by reduction of the pentahalogens with hydrogen, the dihalogen compounds do not exist. Spectroscopically, the monochloride (NbCl) has been observed at high temperatures. The fluorides of niobium can be used after its separation from tantalum. The niobium pentachloride is used in organic chemistry as a Lewis acid in activating alkenes for the carbonyl-ene reaction and the Diels-Alder reaction. The pentachloride is also used to generate the organometallic compound niobocene dichloride ((C5H5) 2NbCl2), which in turn is used as a starting material for other organoniobium compounds.binary compounds of niobium include niobium nitride (NbN), which becomes a superconductor at low temperatures and is used in detectors for infrared light, and niobium carbide, an extremely hard, refractory, ceramic material, commercially used in tool bits for cutting tools. The compounds niobium-germanium (Nb3Ge) and niobium-tin (Nb3Sn), as well as the niobium-titanium alloy, are used as a type II superconductor wire for superconducting magnets. Niobium sulfide as well as a few interstitial compounds of niobium with silicon are also known. br/>
to estimates, niobium is 33rd on the list of the most common elements in the Earth s crust with 20 ppm. The abundance on Earth should be much greater, but the missing niobium may be located in the Earth s core due to the metal's high density. The free element is not found in nature, but it does occur in minerals. Minerals that contain niobium often also contain tantalum, for example, columbite ((Fe, Mn) (Nb, Ta) 2O6), columbite-tantalite (or coltan, (Fe, Mn) (Ta, Nb) 2O6) and pyrochlore (( Na, Ca) 2Nb2O6 (OH, F)). Columbite-tantalite minerals are most usually found as accessory minerals in pegmatite intrusions, and in alkaline intrusive rocks. Less common are the niobates of calcium, uranium, thorium and the rare earth elements such as pyrochlore and euxenite ((Y, Ca, Ce, U, Th) (Nb, Ta, Ti) 2O6). These large deposits of niobium have been found associated with carbonatites (carbonate-silicate igneous rocks) and as a constituent of pyrochlore.two largest deposits of pyrochlore were found in the 1950s in Brazil and Canada, and both countries are still the major producers of niobium mineral concentrates. The largest deposit is hosted within a carbonatite intrusion at Araxá, Minas Gerais Brazil, owned by CBMM (Companhia Brasileira de Metalurgia e Mineração); the other deposit is located at Catalão, Goiás owned by Ang...
