A solution and solid state study of niobium complexes University of ...
A solution and solid state study of niobium complexes University of ... A solution and solid state study of niobium complexes University of ...
Chapter 2 Table 2.2: Stereochemistries and oxidation states of niobium. 2,4 Oxidation state Coordination number Geometry Complex Nb -3 (d 8 ) 5 Trigonal bipyramidal [Nb(CO)5] 3- Nb -1 (d 6 ) 6 Octahedral [Nb(CO)6] - Nb 0 (d 5 ) 6 π Complex Nb(η 6 -mes)2 Nb +1 (d 4 ) 7 π Complex (C5H5)Nb(CO)4 Nb +2 (d 3 ) Nb +3 (d 2 ) Nb +4 (d 1 ) Nb +5 (d 0 ) 4 Square planar NbO 6 Trigonal prismatic NbS 6 Octahedral NbCl2(py)4 6 Trigonal prismatic LiNbO2 6 Octahedral Nb2Cl6(SMe2)3 8 Dodecahedral K5[Nb(CN)8] 6 Octahedral [Nb(Cl)6] 2- 7 Distorted pentagonal bipyramidal K3NbF7 7 Capped octahedron NbCl4(PMe3)3 8 Square antiprismatic Nb(β-dike)4 8 Dodecahedral K4Nb(CN)8·2H2O 8 π Complex Cp2NbMe2 4 Tetrahedral ScNbO4 5 Trigonal bipyramidal NbCl5 (g) 5 Distorted tetragonal pyramid Nb(NMe2)5 5 Square pyramidal [Nb(NMe2)5] 6 Octahedral NbOCl3 6 Trigonal prismatic [Nb(S2C6H4)3] - 7 Distorted pentagonal bipyramidal NbO(S2CNEt2)3 7 Capped Trigonal prismatic [NbF7] 2- 8 Bicapped trigonal prismatic [Nb(trop)4] + 8 Dodecahedral [Nb(O2)4] 3- 8 Square antiprismatic [NbF8] 3- 7
2.1.2 Uses Chapter 2 Niobium has a variety of useful properties; not only for the chemical industry, but also for the steel-, nuclear energy- and electronics industries. In most of the applications where tantalum or niobium can be used, tantalum is at present preferred because of its lower cost and due to the fact that it is slightly more resistant to chemical corrosion than niobium. Table 2.3: Uses of niobium. 5 Niobium Product Niobium oxide Application Benefits - Camera lenses. - Coating on glass for computer screens. - Ceramic capacitors. - Manufacture of lithium niobate for surface acoustic wave filters. Niobium carbide Cutting tool compositions. Niobium powder Niobium metal Ferro-niobium Niobiumtitanium and niobium-tin alloys Niobium capacitors for electronic circuits. Chemical processing equipment. Niobium additive to high strength low alloy steel and stainless steel. Superconducting magnetic coils in magnetic resonance imagery (MRI). 8 - High index of refraction. - High dielectric constant. - Increase light transmittance. High temperature deformation and controls grain growth. High dielectric constant, stability of oxide dielectric. Corrosion resistance. Weight reduction and increased strength and toughness due to grain refining. Very low electrical resistance of alloy wire at low temperatures. Niobium has good high temperature strength and when alloyed with other metals it has improved strength at high temperatures. Ferro-niobium is a mixture of iron and niobium and is used as an additive to improve the strength and corrosion resistance of steel. High purity ferroniobium is used in superalloys for applications as heat- resisting and combustion equipment such as jet engine and missile components. 6 5 D. L. Kepert, The Early Transition Metals, Academic Press, London, 142, 1972. 6 D. J. Soisson, J. J. McLafferty, J. A. Pierret, Ind. Eng. Chem., 53, 11, 861, 1961.
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Chapter 2<br />
Table 2.2: Stereochemistries <strong>and</strong> oxidation <strong>state</strong>s <strong>of</strong> <strong>niobium</strong>. 2,4<br />
Oxidation<br />
<strong>state</strong><br />
Coordination<br />
number<br />
Geometry Complex<br />
Nb -3 (d 8 ) 5 Trigonal bipyramidal [Nb(CO)5] 3-<br />
Nb -1 (d 6 ) 6 Octahedral [Nb(CO)6] -<br />
Nb 0 (d 5 ) 6 π Complex Nb(η 6 -mes)2<br />
Nb +1 (d 4 ) 7 π Complex (C5H5)Nb(CO)4<br />
Nb +2 (d 3 )<br />
Nb +3 (d 2 )<br />
Nb +4 (d 1 )<br />
Nb +5 (d 0 )<br />
4 Square planar NbO<br />
6 Trigonal prismatic NbS<br />
6 Octahedral NbCl2(py)4<br />
6 Trigonal prismatic LiNbO2<br />
6 Octahedral Nb2Cl6(SMe2)3<br />
8 Dodecahedral K5[Nb(CN)8]<br />
6 Octahedral [Nb(Cl)6] 2-<br />
7 Distorted pentagonal<br />
bipyramidal<br />
K3NbF7<br />
7 Capped octahedron NbCl4(PMe3)3<br />
8 Square antiprismatic Nb(β-dike)4<br />
8 Dodecahedral K4Nb(CN)8·2H2O<br />
8 π Complex Cp2NbMe2<br />
4 Tetrahedral ScNbO4<br />
5 Trigonal bipyramidal NbCl5 (g)<br />
5 Distorted tetragonal pyramid Nb(NMe2)5<br />
5 Square pyramidal [Nb(NMe2)5]<br />
6 Octahedral NbOCl3<br />
6 Trigonal prismatic [Nb(S2C6H4)3] -<br />
7 Distorted pentagonal<br />
bipyramidal<br />
NbO(S2CNEt2)3<br />
7 Capped Trigonal prismatic [NbF7] 2-<br />
8 Bicapped trigonal prismatic [Nb(trop)4] +<br />
8 Dodecahedral [Nb(O2)4] 3-<br />
8 Square antiprismatic [NbF8] 3-<br />
7
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