Primary to secondary sphere coordination of 15-crown-5 to lanthanide(III) chlorides: structural analysis of [MCl₃(15-crown-5)] (M=La, Ce) and [Er(OH₂)₈]Cl₃·15-crown-5

Abstract

Complexes of LaCl₃·7H₂O and CeCl₃·7H₂O directly coordinated to 15-crown-5 were prepared by placing the reactants in 3∶1 CH₃CN∶CH₃OH on opposite sides of a fine porosity glass frit in a U-shaped cell and passing a 10 μA current through the cell. The crystal structures of the two anhydrous 8-coordinate complexes, [MCl₃(15-crown-5)] (M=La, Ce) have been determined. Each contains the lanthanide in a bicapped trigonal prismatic geometry. The two complexes are isostructural crystallizing in the monoclinic space groupP2₁/c with (at 20°C) for M=La:a=8.217(8),b=14.298(2),c=14.341(9) Å, β=104.79(8)°, andD _calc=1.90 g cm⁻³ forZ=4; for M=Ce:a=8.208(9),b=14.263(6),c=14.270(8) Å, β=104.74(7)°, andD _calc=1.92 g cm⁻³ forZ=4. Direct reaction of ErCl₃·6H₂O with 15-crown-5 in 3∶1 CH₃CN∶CH₃OH resulted in the crystallization of the second sphere hydrogen bonded complex [Er(OH₂)₈]Cl₃·15-crown-5. This complex is monoclinic,P2₁/n with (at 18°C)a=9.193(3),b=17.235(9),c=15.216(5) Å, β=92.48(3)°, andD _calc=1.76 g cm⁻³ forZ=4. The Er³⁺ ion is dodecahedral.