The nine compounds L,GaX3 where L is Et2O, Me2S, or Et2S and X is Cl, Br, or I have been prepared, most of them for the first time. Thermochemical data have been obtained on the tribromide and tri-iodide complexes and the results, together with known data on the trichloride complexes, are interpreted in terms of steric and polarisability effects. The donor strength of nitrogen, oxygen, and sulphur towards all three trihalides follows the sequence N > S > O. For each ligand the sequence of acceptor strengths is GaCl3 > GaBr3 > Gal3.
