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Issue 3, 2006
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Synthesis and structural characterisation of [TpMe2Nb(CH3)2(CH3C[triple bond, length as m-dash]CCH3)] and [TpMe2NbCl(CH3)(CH3C[triple bond, length as m-dash]CCH3)]: is there an intrinsic α-agostic interaction in alkyl complexes of the [TpMe2Nb(alkyne)] moiety?

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Abstract

The methyl complexes [TpMe2Nb(CH3)2(CH3C[triple bond, length as m-dash]CCH3)] (2) and [TpMe2NbCl(CH3)(CH3C[triple bond, length as m-dash]CCH3)] (3) have been prepared from the corresponding dichloride, and their structures investigated by X-ray diffraction. In each case, the Nb–CH3 moiety displays a normal geometry in comparison with other methylniobium derivatives, with no evidence for the structural distortions which attend an α-agostic interaction. The NMR spectra of 2 and 3, including those of the CH2D isotopomers, also point to a conventional methyl–metal complex, with no isotopic perturbation of resonance which can signal agostic behaviour. Likewise, the IR spectra of the CH3, CH2D and CD3 isotopomers of 2 and 3 indicate a conventional bonding situation, although the asymmetric Nb–CH3 potential leads to two distinct νisCD modes in the CH2D spectrum. Taken together, these results lead us to conclude that there is no intrinsic α-agostic interaction in the methyl complexes 2 and 3, and that the α-agostic structures deduced for their longer chain alkyl congeners are predominantly the result of steric interactions between the alkyl moiety and the bulky TpMe2 ligand.

Graphical abstract: Synthesis and structural characterisation of [TpMe2Nb(CH3)2(CH3C [[triple bond, length as m-dash]] CCH3)] and [TpMe2NbCl(CH3)(CH3C [[triple bond, length as m-dash]] CCH3)]: is there an intrinsic α-agostic interaction in alkyl complexes of the [TpMe2Nb(alkyne)] moiety?

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Publication details

The article was received on 19 Oct 2005, accepted on 09 Jan 2006 and first published on 25 Jan 2006


Article type: Paper
DOI: 10.1039/B514820K
New J. Chem., 2006,30, 409-415

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    Synthesis and structural characterisation of [TpMe2Nb(CH3)2(CH3C[triple bond, length as m-dash]CCH3)] and [TpMe2NbCl(CH3)(CH3C[triple bond, length as m-dash]CCH3)]: is there an intrinsic α-agostic interaction in alkyl complexes of the [TpMe2Nb(alkyne)] moiety?

    E. Teuma, M. Etienne, B. Donnadieu and G. S. McGrady, New J. Chem., 2006, 30, 409
    DOI: 10.1039/B514820K

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