Z. Naturforsch. 2014, 69b, 1321 – 1332
Structures of Tetrasilylmethane Derivatives C(SiXMe2)4 (X = H, F, Cl, Br) in the Gas Phase and their Dynamic Structures in Solution
Derek A. Wann1, Stuart Young1, Karin Bätz2, Sarah L. Masters3, Anthony G. Avent4, David W. H. Rankin5, and Paul D. Lickiss2
1 Department of Chemistry, University of York, Heslington, York, UK YO10 5DD
2 Department of Chemistry, Imperial College London, London, UK SW7 2AZ
3 Department of Chemistry, University of Canterbury, Private Bag 4800, Christchurch 8140, New Zealand
4 Department of Chemistry, School of Life Sciences, University of Sussex, Falmer, Brighton, UK BN1 9QJ
5 School of Chemistry, University of Edinburgh, West Mains Road, Edinburgh, UK EH9 3JJ
Reprint requests to Dr. D. A. Wann. E-mail: derek.wann@york.ac.uk
Received July 8, 2014 / published online December 19, 2014
Dedicated to Professor Hubert Schmidbaur on the occasion of his 80th birthday
The structures of the molecules C(SiXMe2)4 (X = H, F, Cl, Br) have been determined by gas electron diffraction (GED). Ab initio calculations revealed nine potential minima for each species, with significant ranges of energies. For the H, F, Cl, and Br derivatives nine, seven, two, and two conformers were modelled, respectively, as they were quantum-chemically predicted to be present in measurable quantities. Variable-temperature 1H and 29Si solution-phase NMR studies and, where applicable, 13C NMR, 1H/29Si NMR shift-correlation, and 1H NMR saturation-transfer experiments are reported for C(SiXMe2)4 (X = H, Cl, Br, and also I). At low temperature in solution two conformers (one C1-symmetric and one C2-symmetric) are observed for each of C(SiXMe2)4 (X = Cl, Br, I), in agreement with the isolated molecule ab initio calculations carried out as part of this work for X = Cl, Br. C(SiHMe2)4 is present as a single C1-symmetric conformer in solution at the temperatures at which the NMR experiments were performed.
Key words: Silyl Methane Derivatives, Gas Electron Diffraction, Variable-Temperature NMR
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