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Stabilisation of high oxidation-state niobium using 'electron-rich' bicyclic-guanidinates

Stabilisation of high oxidation-state niobium using 'electron-rich' bicyclic-guanidinates
Stabilisation of high oxidation-state niobium using 'electron-rich' bicyclic-guanidinates

Synthetic procedures to high oxidation-state complexes of niobium incorporating the bicyclic guanidinate 1,3,4,6,7,8-hexahydro-2H-pyrimido[1,2-a] pyrimidinate, [hpp]-, are described. The ligand source was either the N-trimethylsilylated guanidine or the lithium guanidinate and the reaction proceeded via elimination of trimethylsilylchloride or transmetallation from NbCl5, respectively. A 1:1 ratio of reagents afforded the mono-ligand product, Nb(hpp)Cl4 (1) and crystallisation from acetonitrile afforded the solvated species Nb(hpp)Cl4(MeCN) (1a), demonstrating the ability of the metal centre in 1 to bind small substrate molecules. A 2:1 ratio of lithium guanidinate to NbCl5 resulted in formation of the seven-coordinate, bis-ligand compound, Nb(hpp)2Cl3 (2). These products represent the first examples of guanidinate compounds in which niobium is stable in the +5 oxidation-state, believed to result from enhanced electron donation caused by the bicyclic framework of the ligand. The molecular structures of 1, 1a and 2 are reported, presenting for the first time an opportunity to describe bonding parameters within compounds of this type.

Crystal structure, Guanidinate, Niobium
0022-328X
2315-2321
Soria, Delia B.
11f39b44-c185-4154-8ae1-b2deee57dbab
Grundy, Joanna
0bc72187-8dce-41fc-b809-93a6adbe0980
Coles, Martyn P.
4cb5ee08-daf9-4b58-9627-61732e0a818b
Hitchcock, Peter B.
4c0fe381-c3e8-452c-a284-fe14acd3b748
Soria, Delia B.
11f39b44-c185-4154-8ae1-b2deee57dbab
Grundy, Joanna
0bc72187-8dce-41fc-b809-93a6adbe0980
Coles, Martyn P.
4cb5ee08-daf9-4b58-9627-61732e0a818b
Hitchcock, Peter B.
4c0fe381-c3e8-452c-a284-fe14acd3b748

Soria, Delia B., Grundy, Joanna, Coles, Martyn P. and Hitchcock, Peter B. (2005) Stabilisation of high oxidation-state niobium using 'electron-rich' bicyclic-guanidinates. Journal of Organometallic Chemistry, 690 (9), 2315-2321. (doi:10.1016/j.jorganchem.2005.02.033).

Record type: Article

Abstract

Synthetic procedures to high oxidation-state complexes of niobium incorporating the bicyclic guanidinate 1,3,4,6,7,8-hexahydro-2H-pyrimido[1,2-a] pyrimidinate, [hpp]-, are described. The ligand source was either the N-trimethylsilylated guanidine or the lithium guanidinate and the reaction proceeded via elimination of trimethylsilylchloride or transmetallation from NbCl5, respectively. A 1:1 ratio of reagents afforded the mono-ligand product, Nb(hpp)Cl4 (1) and crystallisation from acetonitrile afforded the solvated species Nb(hpp)Cl4(MeCN) (1a), demonstrating the ability of the metal centre in 1 to bind small substrate molecules. A 2:1 ratio of lithium guanidinate to NbCl5 resulted in formation of the seven-coordinate, bis-ligand compound, Nb(hpp)2Cl3 (2). These products represent the first examples of guanidinate compounds in which niobium is stable in the +5 oxidation-state, believed to result from enhanced electron donation caused by the bicyclic framework of the ligand. The molecular structures of 1, 1a and 2 are reported, presenting for the first time an opportunity to describe bonding parameters within compounds of this type.

Full text not available from this repository.

More information

Accepted/In Press date: 25 February 2005
e-pub ahead of print date: 14 April 2005
Published date: 29 April 2005
Keywords: Crystal structure, Guanidinate, Niobium

Identifiers

Local EPrints ID: 426200
URI: http://eprints.soton.ac.uk/id/eprint/426200
ISSN: 0022-328X
PURE UUID: 5f9ec765-a2ef-41fb-b8e3-f4bbddc4e59b

Catalogue record

Date deposited: 16 Nov 2018 17:30
Last modified: 16 Nov 2018 17:30

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