ELECTRON PROTON RESONANCE OF TRANSITION METAL COMPLEXES .7. EPR-APPROACH TO LEWIS ACIDITY OF GROUP 3 HALIDES

Complexes of di-π-cyclopentadienyltitanium chloride (Cp2TiCl) with the trichlorides of Group III elements, having the bridged structure {A figure is presented} show EPR hyperfine interaction of the unpaired electron of the TiIII with the magnetic nuclei of the Group III elements. The hyperfine pattern of 115In(I = 9 2) is reported for the first time. From the isotropic coupling with 11B, 27Al, 69Ga, 71Ga, 115In, the unpaired spin density in the relevant s-orbitals of the Group III elements is estimated. The following series is deduced for the Lewis acidity (electron acceptor ability) of the halides: GaCl3 > BCl3 > AlCl3 > InCl3. The results are considered in the light of published information, and chemical evidence is advanced for the strong acid character of GaCl3. © 1969.