Uranyl complexes with potentially pentadentate ligands. Crystal structure of UO 2{[ o-C 6H 4CHN(CH 2) 3] 2OP(C 6H 5)} and UO 2{[ o-OC 6H 5−C(CH 3)N(CH 2) 2] 2NH}

Abstract

Uranyl(VI) complexes with Schiff bases have been extensively studied [1–3]; using, potentially bi-, ter-, tetra- and pentadentate ligands pentagonal bipyramidal coordination geometries are always obtained. Recently we focused our interest in the preparation of a series of uranyl(VI) complexes with the pentadentate ligands of the type: ▪ This paper deals with the preparation, the properties and the crystal structures of uranyl(VI) complexes with the ligands: ▪ All the complexes can be easily prepared as orange red powder, by reacting the performed Schiff bases with uranyl(VI) nitrate. Crystals of UO 2(L 1) are monoclinic, space group P2 1/ c, Z = 4 with a = 6.32(1), b = 13.22(1), c = 24.14(1) Å; β = 92.61(2)°. In this complex ligand is pentadentate in the equatorial plane of the uranyl ion and the five coordinated atoms form a rather puckered pentagon. Although the molecule has no imposed symmetry, the two wings of the ligands are approximately symmetrical forming dihedral angles of 37 and 40° with the coordination plane. They are also strongly inclined with each other with a dihedral angle of 71°. ▪ Uo 2(L 2) is stable in air and apparently does not change with time. The mass spectrum shows a very intense peak due to the parent P + ion at 699 m/e. During the recrystallization an oxidation of the phosphine group to phosphine oxide occurs; the new complex obtained UO 2(L 2′) has a different i.r. spectrum, especially in the vP-O region, and is non-volatile also under drastic conditions. Crystals of UO 2(L 2′) are orthorhombic, space group Pnma, Z = 4, with a = 10.85(1), b = 14.23(1), c = 16.17(1) Å; the five donor atoms of the ligand are equatorially bonded to the uranyl group to form discrete, monomeric molecules with the seven coordinated metal in the usual distorted pentagonal bipyramidal coordination geometry. The molecule lies across a crystallographic mirror plane which contains the uranyl group and the PhPO fragment. The five coordinated atoms form a puckered pentagon where the oxygen atoms are slightly displaced above and the nitrogen atoms below the equatorial mean plane. ( see next page)