ORGANOMAGNESIUM CHEMISTRY - NEARLY 100 YEARS BUT STILL FASCINATING

Victor Grignard discovered his famous reaction, the synthesis of organomagnesium halides or Grignard reagents from organic halides and magnesium, in 1900. Up to now, this reaction has proved tremendously useful in organic and organometallic synthesis, and many of the secrets of its formation, structure, and reactivity have been unravelled. Nevertheless, organomagnesium chemistry is still vital and full of surprises. This will be illustrated with a selection of recent developments, admittedly with a strong bias for results from the author's laboratory. The topics presented concern the intermediacy of carbanions during the conversion of organic halides to Grignard reagents, the induction of high coordination numbers of magnesium by (intramolecular) coordination of crown and polyethers which leads to special structures such as organometallic rotaxanes and catenanes as well as to increased reactivity, and finally small alpha,omega-di-Grignard reagents with one, two or three carbon atoms between the two magnesiums, which are of interest both for their unique structures and for their application in the synthesis of metallacycles and metal-carbene complexes.