Issue 2, 2016

Many Mg–Mg bonds form the core of the Mg16Cp *8Br4K cluster anion: the key to a reassessment of the Grignard reagent (GR) formation process?

Abstract

It caused a sensation eight years ago, when the first room temperature stable molecular compound with a Mg–Mg bond (LMgMgL, L = chelating ligand) containing magnesium in the oxidation state +1 was prepared. Here, we report the preparation of a [Mg16Cp*8Br4K] cluster anion (Cp* = pentamethylcyclopentadiene) with 27 Mg–Mg bonds. It has been obtained through the reaction of KCp* with a metastable solution of MgBr in toluene. A highly-resolved Fourier transform mass spectrum (FT-MS) of this cluster anion, brought into vacuum by electrospraying its solution in THF, provides the title cluster's stoichiometry. This Mg16 cluster together with experiments on the metastable solution of MgBr show that: during the formation process of GRs (Grignard reagents) which are involved in most of sophisticated syntheses of organic products, not the highly reactive MgBr radical as often presumed, but instead the metalloid Mg16Cp*8Br4 cluster anion and its related cousins that are the operative intermediates along the pathway from Mg metal to GRs (e.g. Cp*MgBr).

Graphical abstract: Many Mg–Mg bonds form the core of the Mg16Cp*8Br4K cluster anion: the key to a reassessment of the Grignard reagent (GR) formation process?

Supplementary files

Article information

Article type
Edge Article
Submitted
15 Oct 2015
Accepted
26 Nov 2015
First published
26 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, 1543-1547

Many Mg–Mg bonds form the core of the Mg16Cp*8Br4K cluster anion: the key to a reassessment of the Grignard reagent (GR) formation process?

T. Kruczyński, F. Henke, M. Neumaier, K. H. Bowen and H. Schnöckel, Chem. Sci., 2016, 7, 1543 DOI: 10.1039/C5SC03914B

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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