Crystal Structure of Two Different Hydrate Phases of Bis[2,4,6-tri(2-pyridyl)-1,3,5-triazine]cobalt(II) Diiodide

Abstract

The title compound crystallizes at room temperature from aqueous solution as two distinct hydrated phases, both monoclinic and characterized by single-crystal X-ray structure determinations. The dihydrate ('blocks') is C2/c, a 42.58(2), b 9.099(8), c 21.14(1)Ǻ, β 112.12(4)°, Z= 8; R was 0.048 for 3784 'observed' reflections. The c. 3.75 hydrate ('Tetrahydrate'?) ('needles') is P2₁/c, a 9.348(2), b 36.663(8), c 23.071(8)Ǻ, β 93.51(2)°, Z 8; R was 0.050 for 6042 'observed' reflections. There are one and two independent cations in the asymmetric unit of each structure; all cations have the metal atom 'mer' coordinated by a pair of tridentate ligands. In the C2/c phase, Co-N (central) are 2.057(4) and 2.063(4)Ǻ with N-Co-N 175.8(2)°; Co-N (distal) are 2.163(6)-2.187(6)Ǻ. In the P2₁/c phase, in the first cation, Co-N are 2.045(8) and 2.050(7)Ǻ (central) [with N-Co-N, 167.0(3)°] and 2.193(8)-2.216(8)Ǻ (distal), while, in the second, Co-N (central) are 2.030(8) and 2.042(8)Ǻ with N-Co-N, 168.3(3)°; Co-N (distal) are 2.164(8)-2.227(8)Ǻ. These Co-N distances are longer than those observed in the [Co( tpy )₂]²⁺ cations hitherto studied ( tpy = 2,2′:6′,2′-terpyridine), in which the electronic ground state has an appreciable low-spin component.