METHYL METAL(III)-NITROGEN COMPOUNDS WITH AN OLIGOCYCLIC AS WELL AS CAGE STRUCTURES (M(III)=AL,GA,IN)

Tetrameric trimethylsilylimidomethylgallane, (MeGa=NSiMe(3))(4) (Me = CH3), is formed in ca. 60% yield by the reaction of Br2Ga-N(H)SiMe(3) with lithium methanide in a 1:2 ratio. The high melting (278 degrees C ), volatile (MS), and even in the gas phase assoziated compound crysta llizes in the monoclinic space group C2/c with the cell parameters a = 2001.0(4), b = 1011.6(2), c = 1932.2(4) pm, beta = 120.13(2)degrees, and Z = 4 tetramers. The Ga4N4-skeleton is nearly a perfect cube with Ga-N bonds of 199 pm (average) and Ga-N-Ga angles of 90 degrees. Diaza distannetidine, (Me(2)Sn=N(t)Bu)(2) ((t)Bu=C(CH3)(3)) and AlMe(3) (1:1 ) forms in toluene at 45-50 degrees C tetramethylstannane and heterocy clic Me(2)Sn(N(t)Bu)(2)AlMe. In solution and in the solid state a cent rosymmetric dimer (point symmetry C-i) is formed (monoclinic space gro up P2(1)/n, a = 1154.7(3), b = 921.17(12), c = 1463.9(3) pm, beta = 10 1.08(2)degrees, and Z = 2 dimers). The relatively short Al-N (183.1(3) pm) and Sn-N (202.0(3) pm) distances in this tricyclic,system have be en used for a comparitive discussion of M(III)-N bond lengths (M(III) = Al, Ga, In). Therefore, the X-ray structure of the known Ga(N(SiMe(3 ))(2))(3) has been re-investigated at -100 degrees C. At least (MeIn=N (t)Bu)(4) has been prepared from (Me(2)Sn=N(t)Bu)(2) and base-free InM e(3) (1:2 ratio) in toluene at 75-85 degrees C. The NMR, ir, and Raman spectra are compared with the data of the corresponding Al and Ga hom ologues, respectively.