Issue 21, 2003
From the journal:

Dalton Transactions

C–H and C–C agostic interactions in cycloalkyl tris(pyrazolyl)boratoniobium complexes†

Joëlle Jaffart,a   Marcus L. Cole,‡a   Michel Etienne,*a   Meike Reinhold,b   John E. McGrady*b  and  Feliu Maseras*c  

* Corresponding authors

a Laboratoire de Chimie de Coordination du CNRS, UPR 8241, 205 Route de Narbonne 31077, Toulouse, France
E-mail: etienne@lcc-toulouse.fr
Fax: +33 5 61 55 30 03
Tel: +33 5 61 33 31 76

b Department of Chemistry, University of York, York, YO10 5DD, UK
E-mail: jem15@york.ac.uk
Fax: +44 1904 432516
Tel: +44 1904 434539

c Unitat de Quimica Fisica, Edifici Cn, Universitat Autonoma de Barcelona, 08193 Bellaterra, Spain
E-mail: feliu@klingon.uab.es
Fax: +34 93 5812920
Tel: +34 93 5812851

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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Article information

DOI
https://doi.org/10.1039/B305296F
Article type
Paper
Submitted
12 May 2003
Accepted
19 Jun 2003
First published
22 Sep 2003

Dalton Trans., 2003, 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, 4057 DOI: 10.1039/B305296F

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