Structures of Co, Pd and Ni complexes with iminopyridine ligands having an hydroxymethyl or acrylate pendant group

Co(II), Pd(II) and Ni(II) complexes with iminopyridine ligands have different coordination structures in the solid state, depending on the metal, pendant group of the pyridyl ring and recrystallization conditions. The iminopyridine ligand having an acrylate group, Ar–NCH-2,6-C5H3N–CH2–OCO–CHCH2 (L1: Ar = 2,6-diisopropylphenyl), forms a Co(II) complex whose metal center has a trigonal pyramidal coordination with two chloride ligands and an N,N’-bidentate ligand L1. Both L1 and the iminopyridine ligand with a CH2OH pendant on the pyridyl ring, Ar–NCH-2,6-C5H3N–CH2–OH (L2: Ar = 2,6-diisopropylphenyl), coordinate to the PdCl2 moiety, giving complexes with a square–planar coordination. The reaction of L1 with [NiBr2(H2O)3] and recrystallization of the products forms crystals which contain mono- and dinuclear complexes with aqua ligands and the N,N’-bidentate ligand. L2 is coordinated to the Ni(II) center as an N,N’,O-tridentate ligand. Recrystallization of the products of the reaction of L2 with [NiBr2(H2O)3] with and without excess H2O in the solution yields crystals of the cationic octahedral complex with two aqua ligands [NiBr(H2O)2(L2)]Br and the neutral square pyramidal complex [NiBr2(L2)], respectively.

Graphical abstractThe coordination fashion of iminopyridine ligands to Co(II), Pd(II) and Ni(II) centers depends on the central metals, pendant groups of the pyridyl ring and recrystallization conditions. The Ni(II) complex with the hydroxy pendant group has a tridentate N,N′,O-coordination fashion in contrast to a bidentate N,N′-coordination of the ligand with the acrylate pendant group.Figure optionsDownload full-size imageDownload as PowerPoint slide