Derivatives of lanthanide salts with carbamide CO(NH 2 ) 2 (Ur) and related ligands are promising as precursors for the preparation of materials demanded in diverse areas of novel technology, in nuclear power engineering, and in the production of materials for medical diagnostics. Therefore, the synthesis and investigation of the structures and properties of these compounds attract considerable attention.Although the investigation of the interaction of rare earth metal halides with carbamide has started more than thirty years ago, the structures of the dis covered complexes remain insufficiently studied and the data on the composition of the compounds are sometimes contradictory [1,2]. The crystalline com plexes of lanthanide iodides LnI 3 ⋅ 4Ur ⋅ 4H 2 O (Ln = La, Nd, Eu, Gd, Dy, Ho, Er, Y) preparatively obtained at room temperature [3] are characterized by the com plex cations [Ln(Ur) 4 (H 2 O) 4 ] 3+ in the structure, and there is no coordination of the iodide ions by the lan thanide atoms. Anhydrous compound SmI 3 ⋅ 8Ur [4] was also synthesized at room temperature, and its structure contains the octa(carbamide)samarium complex cations and uncoordinated out of sphere iodide ions.We have earlier studied the complexes of erbium and lutetium bromides with carbamide [Ln(Ur) 4 (H 2 O) 4 ]Br 3 and [Ln(Ur) 6 (H 2 O) 2 ]Br 3 (Ln = Er and Lu) [5]. The coordination of the ligands in these compounds was found to occur through the oxy gen atoms of the water and carbamide molecules. The coordination polyhedron of the rare earth metal atom is a distorted tetragonal antiprism (coordination num ber 8). The bromide ions are not coordinated and exist in the external sphere. The coordination of four carba mide molecules does not change their planar struc ture, and the fifth and sixth coordinated Ur molecules are distorted: the NCO/OCN dihedral angle differs from 180° (152°-160°).The X ray diffraction analysis of the yttrium chlo ride complexes with carbamide, [Y(Ur) 4 (H 2 O) 4 ]Cl 3 and [Y(Ur) 6 (H 2 O) 2 ]Cl 3 , showed that the coordination of the ligands (carbamide and water) also occurred through the oxygen atoms [6]. As in the case of other rare earth metal bromides, the coordination polyhe dron is a distorted tetragonal antiprism (coordination number 8), the coordination of four Ur molecules does not distort their planar structure, and the fifth and sixth Ur molecules form a dihedral angle between the NCO planes, which differs from 180°. The chlo ride ions are not coordinated by the yttrium atoms and lie in the external sphere.At the same time, the structure of the preparatively obtained lanthanum chloride complex with carbamide showed that its crystals contained the [La(Ur) 6 Cl 2 ] + complex cations and uncoordinated chloride ions [7]. This work is aimed at synthesizing (at room tem perature) and characterizing the structures of the car bamide compounds of yttrium and lanthanum bro mides and erbium chloride. Abstract-New complexes of yttrium and lanthanum bromides and erbium chloride with carbamide (Ur), [Y(Ur) 4 (H 2 O) ...