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 ...
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Chapter 2<br />
was prepared by Tasi et al. 31 They previously also synthesised [Rb4(NbO)2(Si8O21)]<br />
which is isotypic to [Cs4(NbO)2(Si8O21)] which was prepared by Crosnier et al. 32<br />
2.4.8 Cyclopentadienes<br />
Based on the type <strong>of</strong> bonding between metals <strong>and</strong> the cyclopentadienyl moiety,<br />
cyclopentadienyl <strong>complexes</strong> are distinguished into three groups; π-, σ- <strong>and</strong> ionic<br />
<strong>complexes</strong>. The cyclopentadienyl lig<strong>and</strong> is usually firmly bound to metals, making the<br />
C5H5M unit a stable synthetic platform for the development <strong>of</strong> a wide range <strong>of</strong><br />
<strong>complexes</strong> for varied applications. The presence <strong>of</strong> various functional groups<br />
attached to the cyclopentadienyl lig<strong>and</strong> determines both the electronic <strong>and</strong> steric<br />
properties <strong>of</strong> the metal centres <strong>and</strong> alters the reactivity <strong>of</strong> their <strong>complexes</strong>.<br />
Numerous <strong>niobium</strong> <strong>complexes</strong> have been synthesised using cyclopentadienes <strong>and</strong><br />
their derivatives as lig<strong>and</strong>s. 33,34,35 Postigo et al. 36 published a paper on the synthesis<br />
<strong>and</strong> reactivity <strong>of</strong> imido <strong>niobium</strong> <strong>complexes</strong> containing a functionalized<br />
(dichloromethylsilyl)cyclopentadienyl lig<strong>and</strong> in 2007. The products, imidodichloro-<br />
<strong>and</strong> imidochloroamido-<strong>niobium</strong> <strong>complexes</strong> with aminosilylcyclopentadienyl lig<strong>and</strong>s,<br />
were isolated by the reaction <strong>of</strong> NbCl5 with C5H4(SiCl2Me)(SiMe3) followed by the<br />
reaction <strong>of</strong> the resulting product with lithium amide. In 2010, Sánchez-Nieves et al. 37<br />
synthesised neutral <strong>and</strong> cationic monocyclopentadienyl alkyl <strong>niobium</strong> <strong>complexes</strong> with<br />
the chemical formula, [NbCl3(C5H4SiMe3)(OR)] (R = tBu, SiiPr3, 2,6-Me2C6H3).<br />
2.4.9 Phosphates<br />
Phosphates are polyatomic ions with the empirical formula PO4 3- <strong>and</strong> consist <strong>of</strong> one<br />
phosphorus atom surrounded by four oxygen atoms in a tetrahedral arrangement.<br />
Niobium phosphates are generally condensed phases prepared by <strong>solid</strong>-<strong>state</strong><br />
reactions or by reactions in fluxes. 38 A wide variety <strong>of</strong> <strong>niobium</strong> phosphates have<br />
31<br />
J. Tasi, P. Tu, T. Chan, K. Lii, Inorg. Chem., 47, 23, 11223, 2008.<br />
32<br />
M. P. Crosnier, D. Guyomard, A. Verbaere, Y. Piffard, Eur. J. Solid State Inorg. Chem., 27, 435, 1990.<br />
33<br />
M. J. Humphries, M. L. H. Green, R. E. Douthwaite, L. H. Rees, Dalton Trans., 4555, 2000.<br />
34<br />
J. Sánchez-Nieves, L. M. Frutos, P. Royo, O. Castano, E. Herdtweck, M. E. G. Mosquera, Inorg. Chem., 49,<br />
10642, 2010.<br />
35<br />
J. A. Acho, L. H. Doerrer, S. J. Lippard. Inorg. Chem., 34, 2542, 1995.<br />
36<br />
L. Postigo, J. Sánchez-Nieves, P. Royo, Inorg. Chim. Acta, 360, 1305, 2007.<br />
37<br />
J. Sánches-Nieves, V. Tabernero, C. Camejo, P. Royo, J. Organomet. Chem., 695, 2469, 2010.<br />
38<br />
A. Leclaire, M. M. Borel, J. Chardon, B. Raveau, J. Solid State Chem., 111, 26, 1994.<br />
17