Wiley InterScience Backfile Collection 1832-2000
Chemistry and Pharmacology
Lithium trimethylsilyldiazomethanide Li(SiMe3)CN2 reacted with the dialkylaluminium or -gallium halides R2AlCl and R2GaBr [R = CH(SiMe3)2] by the elimination of lithium halide and the formation of the corresponding aluminium or gallium diazo compounds. As shown by a crystal structure determination, the gallium derivative 1 adopts the nitrile imine structure, in which the gallium atom is coordinated by the terminal nitrogen atom of the diazo group. The N-N-C-Si moiety is almost ideally linear with N-N and C-N bond lengths of 125.5 and 115.9 pm on average. In contrast, the diazomethane structure was formed with dialkylaluminium chloride, and the aluminium atom in 2 is attached to the carbon atom of diazomethane. The almost linear N-N-C group (174.1°) has N-N and N-C distances of 120.0 and 126.4 pm, respectively, inverse to that of the gallium derivative. The bonding situations can best be described by the resonance structures R-C≡N+-N--GaR2 for 1 and R2Al-(R)C=N+=N- for 2. The nitrile imine isomer of the aluminium compound could be detected by NMR spectroscopy as a by-product. Both compounds gave dimers in the solid state, a Ga2N2 four-membered heterocycle was formed of 1, while an eight-membered Al2C2N4 heterocycle resulted with 2.
Type of Medium: