The first coordination compound of 6-fluoronicotinate: the crystal structure of a one-dimensional nickel(II) coordination polymer containing the mixed ligands 6-fluoronicotinate and 4,4′-bipyridine

Abstract

A one-dimensional nickel(II) coordination polymer with the mixed ligands 6-fluoronicotinate (6-Fnic) and 4,4′-bipyridine (4,4′-bpy), namely, catena-poly[[diaquabis(6-fluoropyridine-3-carboxylato-κO)nickel(II)]-μ-4,4′-bipyridine-κ2 N:N′] trihydrate], {[Ni(6-Fnic)2(4,4′-bpy)(H2O)2]·3H2O} n , (1), was prepared by the reaction of nickel(II) sulfate heptahydrate, 6-fluoronicotinic acid (C6H4FNO2) and 4,4′-bipyridine (C10H8N2) in a mixture of water and ethanol. The nickel(II) ion in 1 is octahedrally coordinated by the O atoms of two water molecules, two O atoms from O-monodentate 6-fluoronicotinate ligands and two N atoms from bridging 4,4′-bipyridine ligands, forming a trans isomer. The bridging 4,4′-bipyridine ligands connect symmetry-related nickel(II) ions into infinite one-dimensional polymeric chains running in the [1\overline{1}0] direction. In the extended structure of 1, the polymeric chains and lattice water molecules are connected into a three-dimensional hydrogen-bonded network via strong O—H...O and O—H...N hydrogen bonds, leading to the formation of distinct hydrogen-bond ring motifs: octameric R 8 8(24) and hexameric R 8 6(16) loops.

Synthesis and crystal structure of a 6-chloronicotinate salt of a one-dimensional cationic nickel(II) coordination polymer with 4,4′-bipyridine

“…The 6-chloronicotinate is not coordinated to the metal ion, but acts as a counter-ion. This was surprising, as we expected to obtain a coordination polymer similar to the one obtained with the closely related 6-fluoronicotinate anion under the same experimental conditions (Politeo et al, 2020). The polymeric {[Ni(4,4 0 -bpy)(H 2 O) 4 ] 2+ } n cation is already well known from the literature, as it crystallizes with various carboxylate anions such as fumarate (Zheng et al, 2002), 3-[4-(carboxymethoxy) phenyl]propanoate (Gong et al, 2009), 3,3 0 -(p-phenylene)diacrylate (Li, 2011), 2-carboxy-4-[4-(3-carboxy-4-carboxylatophenoxy)phenoxy]benzoate (Gao et al, 2016), 3-(4-carboxyphenyl)propanoate (Sun et al, 2013), 1,2,4,5-benzenetetracarboxylate (Wang et al, 2006), 1,4phenylenedipropanoate (Sanram et al, 2016) and 2,3naphthalenedicarboxylate (Hu & Zhang, 2010).…”

“…The crystal structures of only three metal complexes of 6-chloronicotinate (6-Clnic) are known so far (Xia et al, 2012a,b;Li et al, 2006). Recently, we have reported the synthesis, crystal structure and properties of a one-dimensional nickel(II) coordination polymer with mixed ligands: 6-fluoronicotinate as the main ligand and 4,4 0 -bipyridine (4,4 0bpy) as the supporting ligand (Politeo et al, 2020).…”

“…In a continuation of our work on coordination polymers with mixed ligands, we set out to prepare a similar coordination polymer with 6-chlorinicotinate and 4,4 0 -bipyridine, as we did with 6-fluoronicotinate (Politeo et al, 2020). Therefore, we carried out the synthesis and crystallization under the same experimental conditions (in a mixture of water and ethanol and with the same molar ratios of the nickel(II) sulfate and ligands), in hope that the analogous nickel(II) coordination polymer could be obtained.…”

“…We also wanted to examine the influence of the possible weak intermolecular interactions involving the chlorine atoms (e.g. C-HÁ Á ÁCl interactions) on the assembly of the polymeric chains in the crystal packing, especially since the analogous C-HÁ Á ÁF interactions were not found in the crystal packing of the nickel(II) coordination polymer with 6-fluoronicotinate (Politeo et al, 2020). Unfortunately, we were not able to prepare the desired nickel(II) coordination polymer under these experimental conditions, but instead we obtained a 6-chloronicotinate salt of a onedimensional cationic nickel(II) coordination polymer with 4,4 0 -bipyridine, namely the title compound, {…”