Syntheses and crystal structures of the rare-earth complexes [LaI2(THF)(5)](+)I-3(-), [SmCl3(THF)(4)], [ErCl2(THF)(5)](+)[ErCl4(THF)(2)](-), [ErCl3(DME)(2)], and [Na(18-Crown-6)(THF)(2)](+)[YbBr4(THF)(2)](-)

[LaI2(THF)(5)]I-+(3)- (1) is obtained as red crystals from lanthanum powder and 1,2-diiodoethane in THF on exposure to light. Space group Pbcn, Z = 4, lattice dimensions at -83 degrees C: a = 1264.9, b = 2218.9, c = 1199.1 pm, R = 0.031. The lanthanum atom of the cation of 1 is coordinated with the iodine atoms in the axial positions in a pentagonal-bipyramidal way. [SmCl3(THF)(4)] (2) originates as colourless crystals on heating SmCl3 with excess THF in the presence of Me3SiNPEt3. Space group P2(1)/c, Z = 8, lattice dimensions at -50 degrees C: a = 3092.7, b = 826.2, c = 1758.3 pm, beta = 93.85 degrees, R = 0.054. Just like the known sample that crystallizes within the space group F2dd, 2 forms monomeric molecules in which the samarium atom is coordinated with two chlorine atoms in the axial positions in a distorted pentagonal-bipyramidal way. [ErCl2(THF)(5)](+)[ErCl4(THF)(2)](-) (3). Pale pink single crystals of 3 were prepared according to the described method by reaction of erbium powder with trimethylchlorosilane and methanol in THE Space group C2/c, Z = 4, lattice dimensions at -50 degrees C: a = 1246.3, b = 1145.7, c = 2726.0 pm, beta = 91.293 degrees, R = 0.036. The erbium atom of the cation of 3 has a pentagonai-bipyramidal coordination with the chlorine atoms in the axial positions. Within the anion the THF molecules are in trans-arrangement of the octahedrally coordinated erbium atom. [ErCl3(DME)(2)] (4) originates as pink single crystals from 3 with excess boiling 1,2-dimethoxyethane. Space group P2(1)/c, Z = 4, lattice dimensions at -50 degrees C: a = 1137.2, b = 886.5, c = 1561.1 pm, beta = 104.746 degrees, R = 0.032. 4 forms monomeric molecules in which the erbium atom has a pentagonal-bipyramidal surrounding with two chlorine atoms in the axial positions. [Na(18-Crown-6)(THF)(2)](+)[YbBr4(THF)(2)](-) (5) is formed as by-product by the reaction of YbBr3 with NaN(SiMe3)(2) in THF in the presence of 18-crown-6 forming colourless crystals. Space group <P(1)over bar>, Z = 1, lattice dimensions at -70 degrees C: a = 934.6, b = 988.9, c = 1208.0 pm, alpha = 73.82 degrees, beta = 72.98 degrees, gamma = 76.89 degrees, R = 0.029. 5 contains isolated [YbBr4(THF)(2)](-) ions, in which the THF molecules are arranged in trans-position.