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

Article abstract of DOI:10.1139/v97-038

The solid state structures of the compounds GaI₃·PPh₃ and Ga₂I₆·dppe (dppe = 1,2-bis(diphenylphosphino)ethane) have been determined. For the former, in which the GaI₃P core has C_3v symmetry, the structure is trigonal, with a = 14.961 (2) A, c = 16.509(3) A, V = 3199.5(4) A³, Z = 6, space group R3. In Ga₂I₆·dppe, the ligand bridges two GaI₃P centres; the structure is monoclinic, a = 10.196(7) A, b = 15.363(1) A, c = 23.027(9) A, β = 98.735(4)°, V = 3565.1(3.2) A³, Z = 4, space group P2_1/n. The use of ³¹P NMR spectroscopy shows that GaI₃·PPh₃ is slightly dissociated in nonaqueous solution, and the effect of adding Ph₃P or I^- has been investigated. Similar studies with Ga₂I₆·dppe are also reported. In each system, four-coordination at gallium is dominant; an equally important factor is the dimerization of uncomplexed GaI₃ to Ga₂I₆ in these solutions.