Structural studies in metal–purpurate complexes. Part 4. The crystal structures of aquabis(purpurato)lead(II) and aquabis(purpurato)lead(II) trihydrate

Abstract

The crystal structures of two purpurate complexes of stoicheiometry [PbL₂]·4H₂O (1) and [PbL₂]·H₂O (2)(L = purpurate) have been determined at 295 K by X-ray diffraction and refined by least squares to R 0.063 (3 405 ‘observed’ reflections) and 0.083 (2 164 ‘observed’ reflections) resoectively. Crystals of (1) are triclinic, space group P, a= 12.593(7), b= 11.393(5), c= 10.274(3)Å, α= 115:38(3), β= 102.98(4), γ= 103.67(4)°, Z= 2. Crystals of (2) are monoclinic, space group P2₁/n, a= 16.63(1), b= 18.72(2), c= 6.981 (2)Å, β= 100.16(5)°, Z= 4. In each case, the lead atom is eight-co-ordinated 6; two tridente purpurate ligand sites, a water molecule, and an oxygen atom from a neighbouring ligand so that dimers are formed in (1) and a polymeric lattice in (2). In (1), the two non-tridentate oxygen atoms are tolerably trans in the co-ordination sphere [Pb-OH₂, 2.52(1); Pb–O(pupurate), 2.74(1)Å; O–Pb–O, 145.1(5)°] with the two tridentate ligands oppbsed [Pb–N, 2.83(1), 2.75(1)Å, N–Pb–N,176.2(4)°; Pb–O, 2.55(1)–2.74(1)Å]. In (2), the two non-tridentate oxygen atoms are more nearly cis[Pb–OH₂, 2.92(2), Pb–O(purourate), 2.77(2)Å; O–Pb–O, 98.3(5)°] as are the two tridentate ligand sites [Pb–N, 2.66(2), 2.67(2)Å, N–Pb–N, 93.6(5)°; Pb–O, 2.48(2)–2.78 (1)Å].