Crystal structure of Tetraaqua(ethylenediamine)nickel(II) sulfate dihydrate and of Tetraaqua(2,2'-bipyridyl)nickel(II) sulfate dihydrate

Abstract

The crystal structures of the title compounds, [Ni(OH₂)₄(en)] [SO₄].2H₂O, (1), and [Ni(OH₂)4(bpy)]- [SO₄].2H₂O, (2), have been determined by single-crystal X-ray diffraction methods at 295 K, being refined by full matrix least-squares methods to residuals of 0.028,0.031 for 1852, 4323 independent 'observed' reflections respectively. Crystals of (1) are monoclinic, C2/c, a 9.459(4), b 12.192(7), c 12.294(3) Å, β 119.84(4)º, Z 4. In the cation, Ni-N is 2.061(2) Å; Ni-O (trans to O, N respectively) are 2.106(2), 2.063(2) Å. Instead of being enlarged above 90º as predicted from repulsion theory, the angle between the pair of oxygen atoms trans to nitrogen is diminished, being 87 14(7)º. Crystals of (2) are triclinic, P1, a 11.476(5), b 9.351(5), c 7.793(4) Å, α 77.63(4), β 83.52(3), γ87.40(4)º, Z 2. In the cation, Ni-N are both 2.063(2) Å. Ni-O (trans to N, O respectively) are 2.060(2), 2.O42(2); 2.O80(2), 2Å. The short Ni-O distance [2.042(2)Å] is associated with the coordination of a trigonal water molecule.