Different Reactivity Patterns in the Reactions of the Homologous Trimethylelement Compounds EMe₃ (E = Al, Ga, In) with Methylhydrazine

Abstract

The trimethylelement compounds EMe3 (E = Al, Ga, In) followed three different reaction courses upon treatment with methylhydrazine, H2N–N(H)Me. AlMe3 reacted at room temperature by releasing 1.5 equiv. methane to yield the sesquihydrazide (Me2Al)3[μ‐NH–N(H)Me]6Al (1), which in the solid state has a hexacoordinate central aluminum atom and six hydrazido groups in the bridging positions to the three terminally arranged AlMe2 groups. Dissociation occurred upon dissolution, and the dialuminum compound Me2Al[μ‐NH–N(H)Me]2Al(Me)[NH–N(H)Me] (2), containing one terminal hydrazido group, was identified unambiguously by NMR spectroscopy. GaMe3 gave a simple adduct, Me3Ga←N(H)Me–NH2 (3), under the same reaction conditions. Boiling toluene was required to initiate a secondary reaction with the release of methane. A bicyclic tetragallium compound, 4, in which a twofold deprotonated hydrazide, [HN–NMe]2–, bridges four gallium atoms, was the result. Each pair of gallium atoms on both sides of the central hydrazinediide ligand is further bridged by the monoanionic hydrazide [HN–N(H)Me]– to yield two annelated, five‐membered Ga2N3 heterocycles. A similar compound, 5, was directly obtained from the reaction of InMe3 with methylhydrazine at room temperature.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)

From tert‐Butylhydrazine Adducts of AlR3 (R = Me, CMe3) to Oligonuclear AlN Cage Compounds – Evidence for a Hydrazine Twist Across an Al3 Triangle

“…[3][4][5][6][7][8] They were found to be monomeric with the sterically low-shielded NH 2 group usually being coordinated to the Group 13 element, despite theoretical calculations indicating this to be the thermodynamically unstable isomer. The thermodynamically favored isomer, in which the more basic N(H)RЈ group is coordinated to the metal atom, could only be substantiated in the case of the corresponding Ga derivative with a small methyl (6) in which four hydrazinediide moieties are bridged by AlMe groups.…”

“…Heating of 6 resulted in the gradual degradation of the N-N bonds and the formal release of 1 or 3 equiv. of nitrene, N-H, to give the unique cage compounds (MeAl) 4 [N(H)-NCMe 3 ] 3 (NCMe 3 ) (7) and (MeAl) 4 [N(H)-NCMe 3 ](NCMe 3 ) 3 (8). The structures of compounds 6-8 may be derived from Al 4 N 4 cubes in which a number of edges (four, three or one) are bridged by nitrogen atoms of hydrazinediido groups.…”

“…[4] The hydrazine adducts were found to decompose spontaneously at room temperature, or upon slight warming, to yield the corresponding hydrazides featuring monoanionic hydrazide groups. [3,4,[6][7][8][9] These hydrazides are usually dimeric, with the exception of the sterically crowded monomeric compounds In[N(SiMe 3 )-NMe 2 ] 3 [10] and Me 3 C-Al[N(SiMe 3 )-N(H)SiMe 3 ] 2 , [11] and show a variety of structural motifs ranging from four-to six-membered heterocycles, [3,4,[6][7][8][9]12,13] and zero, one, or two endocyclic N-N bonds (Scheme 1). Transannular repulsion between partially charged metal and nitrogen atoms disfavors the formation of E 2 N 2 heterocycles, whereas electrostatic attraction between metal and nitrogen atoms and steric interactions between the substituents favor the creation of small heterocycles.…”

Reactions of Hydrazines with AlH3·NMe2Et – Formation of Aluminum‐Nitrogen Heterocycles

“…[2] The reactions of organoaluminum, -gallium or -indium compounds with hydrazine derivatives gave simple adducts in the first step, which could be isolated and characterized in several cases. [3][4][5][6][7][8][9][10] Spontaneous or thermally induced secondary reactions afforded the corresponding hydrazides by salt elimination, the release of alkanes or elemental hydrogen. These compounds were monomeric only in very few cases, [11][12][13] and usually dimeric formula units were obtained containing four-, five-or six-membered heterocycles.…”

“…[5,7,9,[13][14][15][16][17][18][19][20][21][22][23] Dianionic hydrazinediido ligands form oligomers possessing oligocyclic or cage-like structures. [3,6,10,17,18,[24][25][26] Several effective routes for the synthesis of these hydrazides are known in the literature and comprise the reactions of trialkylelement compounds or dialkylelement hydrides with hydrazines, the salt elimination by treatment of dialkylelement halides with lithium hydrazides and the amide replacement by treatment of aminoalanes with hydrazines. Dianionic hydrazinediido ligands were also obtained by hydroalumination of a 2,3-diazabutadiene derivative or a diazene.…”