MS36-P16 A new double metal oxalate compound with specific structural features Malika Hamadene ( Laboratoire CRI-THER, Faculté de Chimie, USTHB, Alger, Algeria) Hamza Kherfi ( Laboratoire CRI-THER, Faculté de Chimie, USTHB, Alger, Algeria) Fadila Balegroune ( Laboratoire CRI-THER, Faculté de Chimie, USTHB, Alger, Algeria)email: mal_hamadene@hotmail.comOnly a very few examples of double oxalate compounds with Li have been reported in the litterature [1,2]. In continuation of our crystallographic research about the coordination compounds [3], we have chosen to focus on mixed oxalate with Li atoms and 3d element. Pink single crystals with the Cr element have been obtained. Optical, thermal and RX analysis have lead to the formula [LiCr(C2O4)2(H2O)4]n and space group C2/m. In this structure, both metal atoms in special positions are coordinated to two equivalent water molecules in axial sites and four equivalent O atoms from coplanar oxalate groups. The crystal structure consists of infinite and linear chains of trans-Cr(O2)4(Ow2)2 and trans-Li(O1)4(Ow1)2 octahedra µ2-bridged by oxalate groups, and  propagating along [101] direction. The Ow1 atoms around the Li atom are disordered over two positions separated by 0.5259 (6) Å, due to the wagging in the (101) mirror plane. Taking into account of the 2/m imposed symmetry of both metallic elements, the unit cell may be described as an unconventional pseudo face-centered monoclinic cell. In this one-dimensional coordination polymer, R44 (12) H rings are present between the parallel chains to stabilize a 2D framework. The UV and IR analysis are agreeing respectively with the trans conformation of Cr (III) octahedral due to the lack of the ruby line  and the symmetry of the bridged ligands. The investigated compound is found to be a precursor of a ternary oxide LiCrO2, deducted from the thermal analysis.

[1] Romero, S.. Mosset, A.; Trombe, J.C. (1995) Eur. JU ; Solid State Inorg. Chem. 32, 11, 1053-1063.

[2] Declercq, J.P.; Feneau-Dupont, J.; Ladrière, (1995) Polyhedron, 14, 1943-1952

[3] Benhacine, M.A., Hamadène M., Bouacida S., Mérazig H. (2016). Acta Cryst. C72, 243-250

Keywords: 1D polymer ; O atoms disorder ; H rings