Synthesis and characterization of [Me2M-μ-N(H)NMe2]2 (M = Al, Ga). Crystal structure of trans [Me2Al-μ-N(H)NMe2]2

Adducts of organogallium chlorides with hydrazines and the formation of dimeric dialkylgallium hydrazides possessing different ring sizes

“…The last one splitted into two very narrow resonances upon cooling to 285 K. Upon warming, the signals of the tert-butyl groups attached to gallium coincided at about 330 K, those of the N-H protons gave two resonances at about 340 and 350 K, respectively. The activation barrier for the exchange process was estimated [16] to be about 70 kJ/mol, which is similar to values reported before [2,3]. The relative intensities of the NMR signals of the two species at lower temperature (200-320 K) remain constant and verify an almost equimolar distribution (average integration ratio 1-1.2).…”

“…Quantum-chemical calculations on the aluminum compounds revealed that the five-membered Al 2 N 3 heterocycles are the most favourable ones [12]. While NMR spectroscopic investigations of the aluminum hydrazides verified the preservation of the solid state structures in solution, more complicated spectra were detected with gallium hydrazides, which were interpreted by the occurrence of cis/trans isomers with respect to the arrangement of the N-N or N-H bonds [2,3,5]. This isomerization process should proceed by the opening of one Ga-N bond in the ring.…”

“…Generally, they were obtained by the treatment of trialkylgallium compounds [2][3][4][5][6] or stable gallium trihydride adducts [7] with different alkylhydrazines, by the reactions of dialkylgallium chlorides with lithium hydrazides [6][7][8] or by the replacement reaction between a hydrazine derivative and a gallium amide [9]. In some cases, gallium hydrazine adducts could be isolated as stable intermediates [5,6,10].…”

“…All remaining dialkylgallium hydrazides published so far contain the same structural motif in their molecular centres consisting of a four-membered Ga 2 N 2 heterocycle and two exocyclic N-N bonds. In contrast, the homologous dialkylaluminum hydrazides show a broader variability of structures with four- [2,3,11], five- [12] and six-membered heterocycles [12][13][14] and none, one, or two endocyclic N-N groups, respectively (Scheme 1). The respective structural motif seems to be determined by the steric demand of the substituents 0022-328X/$ -see front matter Ó 2005 Elsevier B.V. All rights reserved.…”

Synthesis and X-ray crystallographic structures of [HGa(NMe2)2]2 and [PhGa(NHNMe2)2]2, and room-temperature conversions of [HGa(NMe2)2]2 to (HGaNH)n and (HGaNMe)n

“…These resonances were attributed to an isomer of 2 with one or more cis ligand orientations on gallium or bridging nitrogen atoms. It was reported that both trans and cis isomers were present in solutions for known gallium hydrazide derivatives including (Me 2 GaNHNMe 2 ) 2 [12] and (Me 2 GaNHNPh 2 ) 2 [13].…”