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Benjamin, S.L. 
ORCID: 0000-0002-5038-1599, Chang, Y.-P., Hector, A.L., Jura, M., Levason, W., Reid, G. and Stenning, G.,
2016.
Niobium tetrahalide complexes with neutral diphosphine ligands.
Dalton Transactions, 45, pp. 8192-8200.
ISSN 1477-9226
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Abstract
The reactions of NbCl4 with diphosphine ligands o-C6H4(PMe2)2, Me2PCH2CH2PMe2 or Et2PCH2CH2PEt2 in a 1:2 molar ratio in MeCN solution produced eight-coordinate [NbCl4(diphosphine)2]. [NbBr4(diphosphine)2] (diphosphine = o-C6H4(PMe2)2 or Me2PCH2CH2PMe2) were made similarly from NbBr4. X-ray crystal structures show that [NbCl4{o-C6H4(PMe2)2)2}] has a dodecahedral geometry but the complexes with dimethylene backboned diphosphines are distorted square antiprisms. The Nb-P and <P-Nb-P angles are very similar in the two types, but Nb-Cl distances are ~ 0.1Å longer in the square antiprismatic complexes. These paramagnetic (d1) complexes were also characterised by microanalysis, magnetic measurements, IR and UV-visible spectroscopy. Using a 1:1 molar ratio of NbCl4 : diphosphine (diphosphine = Me2PCH2CH2PMe2, Et2PCH2CH2PEt2, Cy2PCH2CH2PCy2 and Ph2PCH2CH2CH2PPh2) afforded [NbCl4(diphosphine)] and [NbBr4(Me2PCH2CH2PMe2)] was obtained similarly. These 1 : 1 complexes are unstable in solution, preventing X-ray crystallographic study, but based upon their diamagnetism, IR, UV-visible and 31P{1H} NMR spectra they are formulated as halide-bridged dimers [(diphosphine)X2Nb(μ-X)4NbX2(diphosphine)] with single Nb-Nb bonds and chelating diphosphines. The Nb(IV) complexes are prone to hydrolysis and oxidation in solution and the structures of the Nb(V) complexes [NbBr4(Me2PCH2CH2PMe2)2][NbOBr4(MeCN)] with a dodecahedral cation, and [{NbOCl3{Et2P(CH2)2PEt2}}2{μ-Et2P(CH2)2PEt2}] which contains seven-coordinate Nb(V) centres with a symmetrical diphosphine bridge are reported. The structure of niobium tetrabromide, conveniently made from NbCl4 and BBr3, is a chain polymer with edge-linked NbBr6 octahedra and alternating long and short Nb-Nb distances, the latter ascribed to Nb-Nb bonds.
| Item Type: | Journal article | ||||
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| Publication Title: | Dalton Transactions | ||||
| Creators: | Benjamin, S.L., Chang, Y.-P., Hector, A.L., Jura, M., Levason, W., Reid, G. and Stenning, G. | ||||
| Publisher: | Royal Society of Chemistry | ||||
| Date: | 12 April 2016 | ||||
| Volume: | 45 | ||||
| ISSN: | 1477-9226 | ||||
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| Divisions: | Schools > School of Science and Technology | ||||
| Record created by: | Jonathan Gallacher | ||||
| Date Added: | 04 May 2016 12:54 | ||||
| Last Modified: | 13 Oct 2017 10:56 | ||||
| URI: | https://irep.ntu.ac.uk/id/eprint/27733 |
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