Dimethylmagnesium revisited.

A compilation of solvent-free homometallic methyl compounds of the type MMex (x = 1-6) is provided and categorised according to their method of characterisation (powder or single crystal X-ray diffraction, gas electron diffraction (GED), reactivity, unconfirmed). Recrystallisation of polymeric [MgMe2]n from excess GaMe3 led to the formation of highly pure [MgMe2]n suitable for single crystal X-ray crystallographic studies. Transient Mg(GaMe4)2 could be detected in excess GaMe3 by NMR spectroscopy, but its isolation as Mg(GaMe4)2 failed. On one occasion tetrameric [Mg(GaMe4)(OMe)]4 could be isolated as a minor co-product. The formation of single-crystalline [MgMe2]n from a saturated ethereal solution could be reproduced as reported earlier by Coates et al. Assessing the reactivity of potassium methoxide methanol adduct toward Mg(AlMe4)2, the protonolysis reaction with MeOH gave unprecedented [Mg(AlMe4){Al(OMe)2Me2}]2 featuring one 8-membered [MgOAlO]2 metalloxane ring and two 4-membered metallacycles.