Spectroscopic and crystallographic studies of phosphino adducts of gallium(III) iodide

The solid state structures of the compounds GaI 3 *PPh 3 and Ga 2 I 6 *dppe ( dppe = 1,2-bis(diphenylphosphino)ethane ) have been determined. For the former, in which the GaI 3 P core has C 3v symmetry, the structure is trigonal, with a = 14.961(2) Å, c = 16.509(3) Å, V = 3199.5(4) Å 3 , Z = 6, space group . In Ga 2 I 6 *dppe, the ligand bridges two GaI 3 P centres; the structure is monoclinic, a = 10.196(7) Å, b = 15.363(1) Å, c = 23.027(9) Å, β = 98.735(4)°, V = 3565.1(3.2) Å 3 Z = 4, space group P2 1/n The use of 31 P NMR spectroscopy shows that GaI 3 *PPh 3 is slightly dissociated in nonaqueous solution, and the effect of adding Ph 3 P or I − has been investigated. Similar studies with Ga 2 I 6 *dppe are also reported. In each system, four-coordination at gallium is dominant; an equally important factor is the dimerization of uncomplexed GaI 3 to Ga 2 I 6 in these solutions. Keywords: gallium(III) iodide, complexes, phosphorus, NMR, crystallography.