The [trans-YCl2(THF)(5)][trans-YCl4(THF)(2)] salt (1) and polymeric [YCl3.2THF](infinity) (2) were prepared by recrystallization of YCl3.3.5THF from tetrahydrofuran (THF) and from dichloromethane, respectively. Both species have been structurally characterized. Complex 1 crystallizes in the space group C2/c with a = 12.503(4) Angstrom, b = 11.493(3) Angstrom, c = 27.212(8) Angstrom, and beta = 91.41(3)degrees. Compound 2 belongs to the space group P $$($) over bar 1 with a = 8.248(3) Angstrom, b = 8.408(3) Angstrom, c = 9.993(4) Angstrom, alpha = 83.89(4)degrees, beta = 67.73(3)degrees, and gamma = 86.02(3)degrees. In the [trans-YCl2-(THF)(5)](+) cation of 1, the yttrium atom is seven-coordinated by five pentagonal oxygen atoms of THF molecules and two trans chlorine atoms. The structure of 2 includes seven-coordinated Y(III) centers (separated by Y...Y distances of 4.422(1) and 4.436(1) Angstrom), which are linked by double chlorine bridges to form the polymeric species. Two THF molecules and one terminal chlorine atom complete the pentagonal bipyramidal coordination sphere of the yttrium atom. Catalytic activity was found for ethylene polymerization by 1 and 2.