The crystal structures of two Ho~(III) complexes with nta (nitrilotriacetic acid) and cdta (trans-1,2- cyclohexanediaminetetraacetic acid) ligands have been reported, respectively. The crystal data are as follows: (a) K_2[Ho(nta)_2(H_2O)] ·5H_2O, monoclinic system, C2/c space group, a = 1.5364(8) nm, b = 1. 2881(7) nm, c = 2.6163(13) nm, β = 96.140(9)°, V = 5.416(5) nm~3, Z = 8, D_c = 1.932 g·cm~(-3), μ = 3.635 mm~(-1), F(000) = 2944, R = 0. 0310, R_w = 0.0675 for 4509 unique reflections and R = 0.0442, R_w = 0. 0707 for all 10336 reflections. The Ho~(III)N_2O_7 part in the complex anion [Ho(nta)_2(H_2O)]~(3-) is a pseudo-monocapped square antiprismatic nine-coordinated structure. (b) NH_4[Ho(cdta)(H_2O)_2]· 4.5H_2O, triclinic system, P1 space group, a = 0.8636(3) nm, b = 1.0072 (3) nm, c = 1.4457(5) nm, α = 88.382(5)°, β = 75.275(5)°, γ = 88. 380(5)°, V = 1.2154(7) nm~3, Z = 2, D_c = 1.657 g/cm~3, μ = 3.315 mm~ (-1), F(000) = 606, R = 0.0283, R_w = 0.0708 for 4203 unique reflections and R = 0.0325, R_w = 0.0730 for all 4595 reflections. The Ho~(III)N_2O_6 part in the complex anion [Ho(cdta) (H_2O)_2]~- is a pseudo square antiprismatic eight-coordinated structure.

Key words: HOLMIUM COMPLEX, nitrilotriacetic acid, CRYSTAL STRUCTURE