Abstract: The crystal structures of the title compounds were determined by single crystal X-ray diffraction. The complexes all crystallize in the monoclinic space group P2₁/c, with Z=4. Lattice parameters are, a=12.160(4)[12.153(4), 12.122(4)]**,b=8.549(3)[8.562(2), 8.550(4)], c=15.425(2)[l5.376(3), 15.293(6)]Å, β=92.55(2)[92.22(2), 91.77(3)]°. The structures were solved by Patterson and Fourier techniques and refined by leastsquares to R=0.032 [0.067, 0.067]. The Ln (Ⅲ) ions (Ln=Pr, Nb, Sm) are 10-coordinated, being bonded to three bidentate nitrate groups and to the four oxygen atoms of the crown ether. The Ln-O distances are in the range 2.49-2.62[2.47-2.62,2.44-2.58]Å(average:2.54[2.53, 2.51]Å).

Key words: Crystall strueture, Complexes of crown ether with rare earth nitralte