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Niobium tetrahalide complexes with neutral diphosphine ligands

Niobium tetrahalide complexes with neutral diphosphine ligands
Niobium tetrahalide complexes with neutral diphosphine ligands
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 distances and <P–Nb–P angles are very similar in the two types, but Nb–Cl distances are ?0.1 Å 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(?-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{?-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
0300-9246
8192-8200
Benjamin, Sophie L.
33433a1a-691e-439e-a277-e7577bde3a1a
Chang, Yao-Pang
9516eba3-1424-411c-8f13-c564cae63407
Hector, Andrew
f19a8f31-b37f-4474-b32a-b7cf05b9f0e5
Jura, Marek
d145b3fa-eec4-47d8-b47c-61a2b616bc8f
Levason, William
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Reid, Gillian
37d35b11-40ce-48c5-a68e-f6ce04cd4037
Stenning, Gavin
1b8ebbf6-4d05-484d-90b3-7d9a76bee911
Benjamin, Sophie L.
33433a1a-691e-439e-a277-e7577bde3a1a
Chang, Yao-Pang
9516eba3-1424-411c-8f13-c564cae63407
Hector, Andrew
f19a8f31-b37f-4474-b32a-b7cf05b9f0e5
Jura, Marek
d145b3fa-eec4-47d8-b47c-61a2b616bc8f
Levason, William
e7f6d7c7-643c-49f5-8b57-0ebbe1bb52cd
Reid, Gillian
37d35b11-40ce-48c5-a68e-f6ce04cd4037
Stenning, Gavin
1b8ebbf6-4d05-484d-90b3-7d9a76bee911

Benjamin, Sophie L., Chang, Yao-Pang, Hector, Andrew, Jura, Marek, Levason, William, Reid, Gillian and Stenning, Gavin (2016) Niobium tetrahalide complexes with neutral diphosphine ligands. Dalton Transactions, 45 (19), 8192-8200. (doi:10.1039/c6dt01099g).

Record type: Article

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 distances and <P–Nb–P angles are very similar in the two types, but Nb–Cl distances are ?0.1 Å 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(?-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{?-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

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Accepted/In Press date: 8 April 2016
e-pub ahead of print date: 12 April 2016
Organisations: Chemistry

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Local EPrints ID: 398640
URI: https://eprints.soton.ac.uk/id/eprint/398640
ISSN: 0300-9246
PURE UUID: 7149aeb4-3684-4fbb-a709-f55420cfd0bb
ORCID for Andrew Hector: ORCID iD orcid.org/0000-0002-9964-2163
ORCID for William Levason: ORCID iD orcid.org/0000-0003-3540-0971
ORCID for Gillian Reid: ORCID iD orcid.org/0000-0001-5349-3468

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Date deposited: 29 Jul 2016 11:56
Last modified: 07 Aug 2019 05:17

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