Preparation of and X-ray crystal structures of tetrahydrofuran-complexed rare earth chlorides; a structurally rich series

Anhydrous lanthanoid metal chlorides LnCl(3)(thf)(N) (Ln = La, Ce, Nd, Sm, n = 2; Ln = Tb, Ho, n = 2.5; Ln = Dy, Tm, n = 2.7; Ln = Gd, Yb, Lu, n = 3; Ln = Er, n = 3.5) have been prepared in excellent yield by the direct reaction of the lanthanoid metal powders with hexachloroethane in tetrahydrofuran (thf), and (Ln = Eu, n = 0.8; Ln = La, n = 1.7; Ln = Pr, n = 2; Ln = Gd: n = 2.5; Ln = Er, n = 3) in good yield except for EuCl3(thf)(0.8) from bulk metal. [YbCL3(thf)(2)](2) was prepared by prolonged treatment of solid YbCl3(thf)(3) with pentane. The X-ray crystal structures of [LnCl(3)(thf)(2)] (Ln = La, Ce or Pr), [LnCL(3)(thf)(3.5)] (Ln = Gd or Er), [YbCl3(thf)(3)] and [LaCl3(thf)(H2O)] have been determined. For [LaCl3(thf)(2)], a square antiprismatic single-stranded polymer, ...La(mu-Cl)(3)(thf)(2)La(mu-Cl)(3)(thf)(2)..., is the first eight-coordinate LnCl(3)(thf)(n) complex. The metal is surrounded by two sets of three bridging chlorines and cis thf oxygens. [LnCl(3)(thf)(2)] (Ln = Ce, Pr) have seven-coordinate structures with doubly chloride-bridged linear chains, ...LnCl(mu-Cl)(2)(thf)(2)LnCl(mu-Cl)(2)(thf)(2)... where the lanthanoid atom exists in a pentagonal bipyramidal environment, the pentagonal bipyramidal plane being defined by four chloride atoms and one oxygen atom of the thf ligand, and the axial positions being occupied by a chloride and a thf oxygen atom. [LnCl(3)(thf)(3.5)] (Ln = Gd, Er) crystallize as discrete ion pairs, [LnCl(2)(thf)(5)](+)[LnCl(4)(thf)(2)](-). The lanthanoid atom in the cation displays pentagonal bipyramidal geometry with two apical chloride atoms and five equatorial thf ligands while the anion has quasi-regular octahedral stereochemistry with trans thf ligands. [LaCl3(thf)(H2O)] displays an eight-coordinate two-dimensional polymeric array with six bridging chlorides per lanthanum atom. Far-infrared spectra have been recorded for a number of products and used as a basis for structural proposals, particularly for products with fractional thf.