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Issue 7, 2012
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New iso-propoxides, tert-butoxides and neo-pentoxides of niobium(V): Synthesis, structure, characterization and stabilization by trifluoroheteroarylalkenolates and pyridine ligands

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Abstract

The synthesis and characterization of nine new heteroleptic alkoxides of niobium is described. Metathesis reactions of Nb2Cl10 with tBuCH2OH and pyridine (py) or 4-dimethylaminopyridine (DMAP) affords monomeric octahedral complexes Nb(OCH2tBu)5py (1) and Nb(OCH2tBu)5DMAP (2), respectively, in high yields (>60%). The same reaction with tBuOH resulted in a chloro functionalized alkoxide Nb(OtBu)4pyCl (3) and could not be pushed to complete removal of remaining Cl ligand. The introduction of a chelating bidental ligand 3,3,3-trifluoro-1-(pyridine-2-yl)propen-2-ol (2-PyCHCOHCF3) (4′′) in the dimeric framework of Nb2(OiPr)10 (4′) produced a heteroleptic, monomeric niobium complex Nb(OiPr)4(2-PyCHCOCF3) (4) with significantly enhanced stability and volatility. As a comparison to (4), five different heteroaryl systems (5–9) with the same side chain have been synthesized and examined in order to understand the influence upon physio-chemical properties. All the new compounds (1–9) have been characterized by microanalysis, variable temperature multinuclear NMR spectroscopy, mass spectrometry, thermal analysis and single crystal X-ray diffraction studies ((3), (4) and (9)). The molecular structure of (3) revealed mononuclear species with Nb atoms present in the distorted octahedral environment of four tBuO, one chloride and one pyridine ligand. Compounds (4) and (9) consisting of four iPrO and a trifluoroheteroarylenolate exhibited a stronger distortion in the molecular geometry due to the rigidity of chelating β-alkenolate moiety.

Graphical abstract: New iso-propoxides, tert-butoxides and neo-pentoxides of niobium(v): Synthesis, structure, characterization and stabilization by trifluoroheteroarylalkenolates and pyridine ligands

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Publication details

The article was received on 03 Sep 2011, accepted on 31 Oct 2011 and first published on 16 Dec 2011


Article type: Paper
DOI: 10.1039/C1DT11668A
Citation: Dalton Trans., 2012,41, 1981-1990
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    New iso-propoxides, tert-butoxides and neo-pentoxides of niobium(V): Synthesis, structure, characterization and stabilization by trifluoroheteroarylalkenolates and pyridine ligands

    L. Appel, R. Fiz, W. Tyrra and S. Mathur, Dalton Trans., 2012, 41, 1981
    DOI: 10.1039/C1DT11668A

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