Abstract A series of rare earth complexes of tributylammonium nitrate was synthesized. The general formula was C 38H 84LnN 9O 18 (Ln La, Ce, Pr, Nd). The IR spectra and thermoanalytical curves of the complexes were studied. The molar conductivities showed them to be 3:1 type electrolytes and ionic crystals. The single-crystal structure of tributylammonium hexanitrate lanthanum was determined using a four-circle X-ray diffractometer. The crystal is monoclinic, space group C 2, with unit cell dimensions a = 1.4983(2) nm, b = 1.6715(7) nm, c = 1.1131(3) nm, β = 91.82(2)°, Z = 2, R = 0.062 and R w = 0.074. Lanthanum is coordinated by 12 oxygen atoms of six bidentate nitrate groups. The polyhedron of the La 3+ ion is a twist bistaggered 3333 stack. The average bond length La-O is 0.2569 nm.