Organometallic compounds of Ga, In and Tl

Organometallic compounds of Ga, In and Tl have been less studied than their Al analogues. The trialkyls do not dimerize and there is a general tendency to diminishing thermal stability with increasing atomic weight of M. There is also 

The triphenyl analogues are also monomeric in solution but tend to associate into chain structures in the crystalline state as a result of weak intermolecular M C interactions GaPh mp 

InPhj mp 208°, TlPha mp 170°. For Ga and In compounds the primary M-C bonds can be cleaved by HX, Xj or MX3 to give reactive halogen-bridged dimers (R2MX)2. This contrasts with the unreactive ionic compounds of T1 mentioned above, which can be prepared by suitable Grignard reactions  

As in the case of organoaluminium compounds, unusual stereochemistries can be imposed by suitable design of ligands. Thus, reaction of GaCb with 3,3, 3 -nitrilotris(propylmagnesium chloride), [N (CH2)3MgCl)3], yields colourless 

Ga and tetrahedral coordination about N. (b) Structure of [MejIn(i) -(Pr NCH2)3 ] — see text for dimensions, (c) Structure of polymeric [Infn -C, ,)]. 

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Many organoaluminium compounds are known which contain 1, 2, 3 or 4 Al-C bonds per A1 atom and, as these have an extensive reaction chemistry of considerable industrial importance, they will be considered before the organometallic compounds of Ga, In and Tl are discussed. 

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