Solid-state structures 8-gallium

Fig. 17. Section of the solid-state structure of a-gallium. The Gaf) structural elements are marked.

Fig. 2.3-18. Molecular structure of 67 (omitting Ph and Me groups) and the corresponding section from the solid-state structure of -gallium.

The solid-state structure of bis(2,6-diphenylphenyl)gallium iodide, (2,6-Ph2C6H3)2GaI, displays the gallium atom in a somewhat distorted trigonal planar environment (C-Ga-C 134.3(3)°). The Ga-I bond distance of 2.550(1) A is unremarkable (Figure 4). 

Perhaps the most telling comparison of (2,6-Ph2CeH3)- is with the closely related, but even more sterically demanding ligand system of 2,6-dimesitylphenyl, (2,6-Mes2C6H3)-. The solid-state structures of both bis(2,6-dimesitylphenyl)gallium... 

In view of the very similar sizes of aluminium and gallium (covalent radii 1.18 A and 1.26 A respectively) it is rather surprising that MCjGa is monomeric in the vapour and liquid states and also in hydrocarbon solvents. Gallium is rather more electronegative than aluminium (Al, 1.61 Ga,1.81) and the lower polarity of the Ga—C bonds may be decisive. Trivinylgallium, however, is dimeric. While the solid state structure of Me3Ga is not known, trimethylindium and trimethyl-thallium crystallize as weakly associated tetramers, in which the planar... 

This complexity can be illustrated with very simple systems. It is known from the solid state that gallium has a tendency to adopt unusual structures as a metal and in some modifications a kind of pairing into primary Ga-Ga units has been observed. This has driven many researchers to attempt to obtain information about the liquid state. Figure 10.18 shows the radial distribution curves of liquid gallimn obtained by X-ray diffraction at three different temperatures [18]. 

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