Gallium amides

Contrary to the usual trend, the covalent radius of gallium is ca. 0.05 A smaller that that of aluminium, which is reflected in Ga—Ga distances which are ca. 0.1 A shorter than the Al—Al distances in metal-metal bonded compounds that carry the same substituents. 

The simplest gallium amides have been generated via direct reaction of the metal with ammonia and trapped in matrices at low temperature. The structure of the primary amide H2GaNH2 is planar with a calculated Ga—N distance of 1.8221 A (cf. 1.7790 A for H2AINH2). Other calculations afford similar values. Under ambient conditions H2GaNH2 is a trimer and displays a six-membered (GaN)3 ring in a chair conformation with a mean Ga-N distance near 1.99 A very similar structure is observed for the 

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Mixed aluminium-gallium amide derivatives have also been reported, as in [H2A1 N-... 

Table 8.1 Metal-nitrogen bond lengths in isoleptic aluminium and gallium amides...

Most gallium amides are dimers which feature a planar (GaN)2 core with Ga—N bond lengths in the range 1.96-2.10 A. As is the case for the monomers many of these... 

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