ORGANOMAGNESIUM CHEMISTRY - NEARLY 100 YEARS BUT STILL FASCINATING

Victor Grignard discovered his famous reaction, the synthesis of organ omagnesium halides or Grignard reagents from organic halides and magne sium, in 1900. Up to now, this reaction has proved tremendously useful in organic and organometallic synthesis, and many of the secrets of i ts formation, structure, and reactivity have been unravelled. Neverthe less, organomagnesium chemistry is still vital and full of surprises. This will be illustrated with a selection of recent developments, admi ttedly with a strong bias for results from the author's laboratory. Th e topics presented concern the intermediacy of carbanions during the c onversion of organic halides to Grignard reagents, the induction of hi gh coordination numbers of magnesium by (intramolecular) coordination of crown and polyethers which leads to special structures such as orga nometallic rotaxanes and catenanes as well as to increased reactivity, and finally small alpha,omega-di-Grignard reagents with one, two or t hree carbon atoms between the two magnesiums, which are of interest bo th for their unique structures and for their application in the synthe sis of metallacycles and metal-carbene complexes.