Stabilisation of High Oxidation-State Niobium Using 'Electron-Rich' Bicyclic-Guanidinates

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). 2278 - 2284. ISSN 0022-328X

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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.

Item Type: Article
Schools and Departments: School of Life Sciences > Chemistry
Depositing User: Martyn Coles
Date Deposited: 06 Feb 2012 20:32
Last Modified: 27 Mar 2012 15:13
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