The crystal structure of catena-poly[(μ2-4,4′-dipyridine-κ2N,N′)-bis(3,5,6-trichloropyridine-2-oxyacetato-κO)-bis(ethanol-κO)nickel(II)], C28H26Cl6N4NiO8

Abstract C28H26Cl6N4NiO8, monoclinic, I2/a (no. 15), a = 15.7577(10) Å, b = 12.6174(7) Å, c = 16.7333(10) Å, β = 99.609(6)Å, V = 3280.3(3) Å3, Z = 4, Rgt(F) = 0.0674, wRref(F2) = 0.1665, T = 291.2(3) K.

dissolved in a mixture of 20 mL of water/ ethanol (V:V = 1:1). Then the pH of the mixture was neutralized with KOH (0.1 mol·L −1 ) to pH = 6.5. After that, the mixed solution was sealed in a 25 mL Teflon reactor and kept under autogeneous pressure at 393 K for 3 days. After cooling to room temperature at a rate of 279 K·h −1 , green block crystals of the title compound were obtained and collected. Yield: 20 mg (16%, based on ligand 3,5,6-Htcpa). Anal. Calcd for C 28 [1] was used for empirical absorption correction using spherical harmonics, implemented in SCALE3 ABSPACK scaling algorithm. Using Olex2 [2], the structure was solved with the ShelXT [3] structure solution program using Intrinsic Phasing and refined with the ShelXL [4] refinement package. The H atoms bonded to C atoms were fixed, with C-H distance of 0.93 Å; and/or positioned geometrically in the riding-model approximation, with C-H distance of 0.97 Å;
Single-crystal X-ray diffraction analysis shows that the asymmetric unit of I includes one half of a Ni II ion, one 3,5,6tcpa ligands, one half of a 4,4′-dipy together with one ethanol molecule.
The µ 2 -4,4′-dipy molecules bridge the neighbouring Ni II ions with their nitrogen atoms to form zigzag chain structure along the a axis. The Ni· · · Ni separation across 4,4′-dipy is 11.452 Å. The adjacent Ni· · · Ni distance parallel to the a axis is 15.758 Å. The 3D crystal packing is constructed by O-H· · · O hydrogen bonding and weak Cl· · · Cl halogen bonding.
Comparing I with [Ni(3,5,6-tcpa) 2 (4,4′-dipy) 1/2]n (II) [44], both of which prepared from the same starting reactants, some important similarities and differences can be found as follows: (i) The structure. They are both 1D polymer. The title structure is a zigzag chain, while II is a linear structure. (ii) The µ 2 -function of 4,4′-dipy. Both 4,4′-dipy join Ni II centers to form the corresponding polymer. (iii) The composition. There are complexed ethonal molecules in I, but absence in II. This is because of the use of the mixed H 2 O-ethanol solvent for synthesis of I, while pure H 2 O solvent for that of II. (iv) The coordination mode of 3,5,6-tcpa. It is monodentate in I, but bidentate in II. (v) The coordination geometry of Ni II ion. It is in octahedron for I, while in tetragonal pyramid for II.
From the above careful disscussion, it was confirmed again that the different synthesis conditions, such as by changing the solvent, greatly affected the composition and structure of complexes. Now, many further attempts on developing new complexes with 3,5,6-Htcpa as the first ligand, for instance by the use of other solvents, introducing other N/O-donor bridging or chelate auxiliary ligands will be gradually implemented.