The influence of the substituent type and position on the topology of 2-D heterometallic sodium–palladium(ii) coordination networks with substituted nicotinate ligands

Abstract

Two 2-D heterometallic sodium–palladium(II) coordination networks with 2-methylnicotinate (2-methylpyridine-3-carboxylate, 2-Menic) and 6-fluoronicotinate (6-fluoropyridine-3-carboxylate, 6-Fnic) ligands, {[Na₂(H₂O)₂(µ-H₂O)₄PdCl₂(µ-2-Menic-N:O′)₂]·2H₂O}_n (1) and {[Na₂(H₂O)₂(µ-H₂O)₄PdCl₂(µ-6-Fnic-N:O′)₂]·2H₂O}_n (2), respectively, were prepared in aqueous solutions (1) or ethanol/water mixtures (2) in the presence of NaHCO₃. Both compounds form 2-D polymeric layers composed of water-bridged sodium ion chains linked by [PdCl₂(2-Menic)₂]²⁻ moieties in 1 or by [PdCl₂(6-Fnic)₂]²⁻ moieties in 2, which exclusively adopt the trans-configuration around the Pd(II) ion. The different positions and electronic properties of 2-Menic and 6-Fnic ligands change the local electrostatic environment of the coordinated Pd(II) ions and influence intermolecular interactions, including the stabilizing R₂²(8) hydrogen-bond motif involving C–H⋯F hydrogen bonds in 2, thereby determining the overall topology of the said 2-D heterometallic sodium–palladium(II) coordination networks.