Detlef Thoennes

Über metallalkyl- und -arylverbindungen : XXIII. Darstellung und kristallstruktur des (methyllithium)4(N,N,N′,N′-tetramethylethylendiamin)2

Abstract Methyllithium and N,N,N′,N′ -tetramethylethylendiamine (tmeda) react with formation of (MeLi) 4 (tmeda) 2 . A single-crystal X-ray diffraction study (tetragonal space group 4 2 / n ; a = b 1149, c 902 pm; 605 reflections; R 0.082) reveals that the methyllithium tetramers persist. These units show almost ideal T n symmetry and are linked through Li—tmeda—Li bridges. Bond distances for LiLi(256–257 pm) and LiC(Me)(223–227 pm) are of particular interest because so far only less accurate values for non-complexed methyllithium were available from powder data.

Über metallalkyl- und -arylverbindungen : XXV. Die kristallstruktur von dimethyl(N,N,N′,N′-tetramethylethylendiamin)magnesium

Abstract Dimethyl(N,N,N′,N′-tetramethylethylenediamine)magnesium is prepared from Me2Mg and N,N,N′,N′-tetramethylethylenediamine (TMEDA), it has been investigated by X-ray diffraction methods (orthorhombic space group Cmca, Z = 8, 879 reflections, R = 0.076). Similarly to Ph2Mg · TMEDA the Mg atom is fourfold coordinated by two methyl groups and the chelate ligand. MgC and MgN distances are very similar in both compounds. Compared to polymeric Me2Mg and Et2Mg the MgC distances in Me2Mg · TMEDA are significantly shorter.