Issue 1, 2016

Synthesis, structure and reactivity of a terminal magnesium fluoride compound, [TpBut,Me]MgF: hydrogen bonding, halogen bonding and C–F bond formation

Abstract

The bulky tris(3-tert-butyl-5-pyrazolyl)hydroborato ligand, [TpBut,Me], has been employed to obtain the first structurally characterized example of a molecular magnesium compound that features a terminal fluoride ligand, namely [TpBut,Me]MgF, via the reaction of [TpBut,Me]MgMe with Me3SnF. The chloride, bromide and iodide complexes, [TpBut,Me]MgX (X = Cl, Br, I), can also be obtained by an analogous method using Me3SnX. The molecular structures of the complete series of halide derivatives, [TpBut,Me]MgX (X = F, Cl, Br, I) have been determined by X-ray diffraction. In each case, the Mg–X bond lengths are shorter than the sum of the covalent radii, thereby indicating that there is a significant ionic component to the bonding, in agreement with density functional theory calculations. The fluoride ligand of [TpBut,Me]MgF undergoes halide exchange with Me3SiX (X = Cl, Br, I) to afford [TpBut,Me]MgX and Me3SiF. The other halide derivatives [TpBut,Me]MgX undergo similar exchange reactions, but the thermodynamic driving forces are much smaller than those involving fluoride transfer, a manifestation of the often discussed silaphilicity of fluorine. In accord with the highly polarized Mg–F bond, the fluoride ligand of [TpBut,Me]MgF is capable of serving as a hydrogen bond and halogen bond acceptor, such that it forms adducts with indole and C6F5I. [TpBut,Me]MgF also reacts with Ph3CCl to afford Ph3CF, thereby demonstrating that [TpBut,Me]MgF may be used to form C–F bonds.

Graphical abstract: Synthesis, structure and reactivity of a terminal magnesium fluoride compound, [TpBut,Me]MgF: hydrogen bonding, halogen bonding and C–F bond formation

Supplementary files

Article information

Article type
Edge Article
Submitted
17 Sep 2015
Accepted
21 Oct 2015
First published
17 Nov 2015
This article is Open Access

All publication charges for this article have been paid for by the Royal Society of Chemistry
Creative Commons BY license

Chem. Sci., 2016,7, 142-149

Synthesis, structure and reactivity of a terminal magnesium fluoride compound, [TpBut,Me]MgF: hydrogen bonding, halogen bonding and C–F bond formation

M. Rauch, S. Ruccolo, J. P. Mester, Y. Rong and G. Parkin, Chem. Sci., 2016, 7, 142 DOI: 10.1039/C5SC03504J

This article is licensed under a Creative Commons Attribution 3.0 Unported Licence. You can use material from this article in other publications without requesting further permissions from the RSC, provided that the correct acknowledgement is given.

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