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Issue 21, 2003
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C–H and C–C agostic interactions in cycloalkyl tris(pyrazolyl)boratoniobium complexes

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Abstract

Cycloalkyl niobium complexes, TpMe2NbX(R)(MeC[triple bond, length as m-dash]CMe) (TpMe2 = hydrotris(3,5-dimethylpyrazolyl)borate; X = Cl, R = c-C3H5 (2a); X = Br, R = c-C3H5 (2b), X = Cl, R = c-C5H9 (3), X = Cl, R = c-C6H11 (4),) have been prepared from TpMe2NbCl2(MeC[triple bond, length as m-dash]CMe). The cyclopropyl complex 2a shows no sign of C–H agostic interactions either in the solid state (X-ray) or in solution. In contrast, the NMR spectra of 3 and 4 are temperature dependent as a consequence of an equilibrium between a major α-agostic species and a minor non-agostic one. Hybrid QM/MM calculations are used to rationalise the behaviour of these cycloalkyl species, and illustrate the subtle interplay of steric and electronic effects in these systems.

Graphical abstract: C–H and C–C agostic interactions in cycloalkyl tris(pyrazolyl)boratoniobium complexes

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Publication details

The article was received on 12 May 2003, accepted on 19 Jun 2003 and first published on 22 Sep 2003


Article type: Paper
DOI: 10.1039/B305296F
Citation: Dalton Trans., 2003,0, 4057-4064
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    C–H and C–C agostic interactions in cycloalkyl tris(pyrazolyl)boratoniobium complexes

    J. Jaffart, M. L. Cole, M. Etienne, M. Reinhold, J. E. McGrady and F. Maseras, Dalton Trans., 2003, 0, 4057
    DOI: 10.1039/B305296F

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